Compounds and methods for inhibiting phosphate transport

ABSTRACT

Compounds having activity as phosphate transport inhibitors, more specifically, inhibitors of intestinal apical membrane Na/phosphate co-transport, are disclosed. The compounds have the following structure (I): 
     
       
         
         
             
             
         
       
     
     including stereoisomers, pharmaceutically acceptable salts and prodrugs thereof, wherein X, Y, R 1  and R 2  are as defined herein. Methods associated with preparation and use of such compounds, as well as pharmaceutical compositions comprising such compounds, are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International PCT PatentApplication No. PCT/US2011/043266, filed Jul. 7, 2011, now pending,which claims the benefit under 35 U.S.C. §119(e) of U.S. ProvisionalPatent Application No. 61/362,133 filed Jul. 7, 2010. The foregoingapplications are incorporated herein by reference in their entireties.

BACKGROUND

1. Field

The present invention is directed to novel phosphate transportinhibitors, more specifically, inhibitors of intestinal apical membraneNa/phosphate co-transport, and methods for their preparation and use astherapeutic or prophylactic agents.

2. Description of the Related Art

Patients with inadequate renal function, hypoparathyroidism, or certainother medical conditions (such as hereditary hyperphosphatemia, Albrighthereditary osteodystrophy, amyloidosis, etc.) often havehyperphosphatemia, or elevated serum phosphate levels (wherein thelevel, for example, is more than about 6 mg/dL). Hyperphosphatemia,especially if present over extended periods of time, leads to severeabnormalities in calcium and phosphorus metabolism, often manifested bysecondary hyperparathyroidism, bone disease and ectopic calcification inthe cardiovascular system, joints, lungs, eyes and other soft tissues.Higher serum phosphorus levels are strongly associated with theprogression of renal failure, cardiovascular calcification and mortalityin end-stage renal disease (ESRD) patients. High-normal serum phosphoruslevels have been associated with cardiovascular events and mortalityamong individuals who have chronic kidney disease (CKD) and among thosewho have normal kidney function (see, e.g., Joy, M. S., P. C.Karagiannis and F. W. Peyerl, Outcomes of Secondary Hyperparathyroidismin Chronic Kidney Disease and the Direct Costs of Treatment, J. Manag.Care Pharm., 13(5):397-411 (2007)) The progression of kidney disease canbe slowed by reducing phosphate retention. Thus, for renal failurepatients who are hyperphosphatemic and for chronic kidney diseasepatients who have serum phosphate levels within the normal range or onlyslightly elevated, therapy to reduce phosphate retention is beneficial.

For patients who experience hyperphosphatemia, calcium salts have beenwidely used to bind intestinal phosphate and prevent its absorption.Different types of calcium salts, including calcium carbonate, acetate,citrate, alginate, and ketoacid salts have been utilized for phosphatebinding. A problem with all of these therapeutics is the hypercalcemia,which often results from absorption of high amounts of ingested calcium.Hypercalcemia causes serious side effects such as cardiac arrhythmias,renal failure, and skin and vascular calcification. Frequent monitoringof serum calcium levels is required during therapy with calcium-basedphosphate binders. Other calcium and aluminum-free phosphate binders,such as sevelamer, a crosslinked polyamine polymer, have drawbacks thatinclude the amount and frequency of dosing required to betherapeutically active. The relatively modest phosphate binding capacityof those drugs in vivo obliges patients to escalate the dose (up to 7grs per day or more). Such quantities have been shown to producegastrointestinal discomfort, such as dyspepsia, abdominal pain and, insome extreme cases, bowel perforation.

An alternative approach to the prevention of phosphate absorption fromthe intestine in patients with elevated phosphate serum levels isthrough inhibition of the intestinal transport system which mediatesphosphate uptake in the intestine. It is understood that phosphateabsorption in the upper intestine is mediated at least in part by acarrier-mediated mechanism which couples the absorption of phosphate tothat of sodium. Inhibition of intestinal phosphate transport will reducebody phosphorus overload. In patients with advanced kidney disease (e.g.stage 4 and 5), the body phosphorus overload manifests itself by serumphosphate concentration above normal levels, i.e. hyperphosphatemia.Hyperphosphatemia is directly related to mortality and morbidity.Inhibition of intestinal phosphate transport will reduce serum phosphateconcentration and therefore improve outcome in those patients. Inchronic kidney disease patients stage 2 and 3, the body phosphorusoverload does not necessarily lead to hyperphosphatemia, i.e. patientsremain normophosphatemic, but there is a need to reduce body phosphorusoverload even at those early stages to avoid associated bone andvascular disorders, and ultimately improve mortality rate. Similarly,inhibition of intestinal phosphate transport would be particularlyadvantageous in patients that have a disease that is treatable byinhibiting the uptake of phosphate from the intestines. Inhibition ofphosphate absorption from the glomerular filtrate within the kidneyswould also be advantageous for treating chronic renal failure.Furthermore, inhibition of phosphate transport may slow the progressionof renal failure and reduce risk of cardiovascular events.

While progress has been made in this field, there remains a need in theart for novel phosphate transport inhibitors. The present inventionfulfills this need and provides further related advantages.

BRIEF SUMMARY

In brief, the present invention is directed to compounds having activityas phosphate transport inhibitors, more specifically, inhibitors ofintestinal apical membrane Na/phosphate co-transport, includingstereoisomers, pharmaceutically acceptable salts and prodrugs thereof,and the use of such compounds to inhibit sodium-mediated phosphateuptake and to thereby treat any of a variety of conditions or diseasesin which modulation of sodium-mediated phosphate uptake provides atherapeutic benefit.

In one embodiment, compounds having the following structure (I) areprovided:

or a stereoisomer, prodrug or pharmaceutically acceptable salt thereof,

wherein:

-   -   X is substituted aryl or substituted heteroaryl;    -   Y is halogen, optionally substituted alkylamino, optionally        substituted alkoxy, optionally substituted thioalkyl, optionally        substituted cycloalkyl, optionally substituted heterocyclyl,        optionally substituted aryl, —O(optionally substituted        cycloalkyl), —O(optionally substituted heterocyclyl) or        —O(optionally substituted aryl);    -   each R₁ is, independently, hydrogen, halogen, C₁₋₆alkyl or        C₁₋₆haloalkyl; and    -   R₂ is hydrogen or optionally substituted C₁₋₆alkyl.

In another embodiment, a pharmaceutical composition is providedcomprising a compound having structure (I), or a stereoisomer,pharmaceutically acceptable salt or prodrug thereof, and apharmaceutically acceptable carrier, diluent or excipient. In furtherembodiments, the pharmaceutical composition further comprises one ormore additional biologically active agents. In more specificembodiments, the additional biologically active agent is selected fromvitamin D₂ (ergocalciferol), vitamin D₃ (cholecalciferol), activevitamin D (calcitriol) and active vitamin D analogs (e.g.doxercalciferol, paricalcitol). In other more specific embodiments, theadditional biologically active agent is a phosphate binder, and thecompound does not interfere with the phosphate binder. For example, incertain embodiments, the phosphate binder is selected from the groupconsisting of Renvela, Renagel, Fosrenol, calcium carbonate, calciumacetate (e.g. Phoslo), MC1-196, Zerenex™, Fermagate, APS1585, SBR-759and PA-21. In other further embodiments, the compound is substantiallyactive as an inhibitor of Na/phosphate co-transport and the Na/phosphateco-transport is mediated by NaPi2b.

In another embodiment, a method of inhibiting phosphate transport in amammal is provided, comprising administering to the mammal an effectiveamount of a compound having structure (I), or a stereoisomer,pharmaceutically acceptable salt or prodrug thereof, or a pharmaceuticalcomposition comprising such compound. In further embodiments, the methodinhibits sodium-mediated phosphate uptake. In other further embodiments,the method is selected from the group consisting of: (a) a method fortreating hyperphosphatemia; (b) a method for treating a renal disease;(c) a method for delaying time to dialysis; (d) a method for attenuatingintima localized vascular calcification; (e) a method for reducing thehyperphosphatemic effect of active vitamin D; (f) a method for reducingFGF23 levels; (g) a method for attenuating hyperparathyroidism; (h) amethod for improving endothelial dysfunction induced by postprandialserum phosphate; (i) a method for reducing urinary phosphorous; (j) amethod for normalizing serum phosphorus levels; (k) a method fortreating proteinura; and (1) a method for reducing serum PTH andphosphate concentrations or levels. In certain embodiments, the renaldisease is chronic kidney disease or end stage renal disease.

In another embodiment, a method of treating hyperphosphatemia in amammal in need thereof is provided, comprising administering to themammal an effective amount of a compound having structure (I), or astereoisomer, pharmaceutically acceptable salt or prodrug thereof, or apharmaceutical composition comprising such compound.

These and other aspects of the invention will be apparent upon referenceto the following detailed description.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments of theinvention. However, one skilled in the art will understand that theinvention may be practiced without these details.

Unless the context requires otherwise, throughout the presentspecification and claims, the word “comprise” and variations thereof,such as, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to”.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, the appearances of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout this specification are not necessarily all referring to thesame embodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

“Amino” refers to the —NH₂ radical.

“Cyano” refers to the —CN radical.

“Hydroxy” or “hydroxyl” refers to the —OH radical.

“Imino” refers to the ═NH substituent.

“Nitro” refers to the —NO₂ radical.

“Oxo” refers to the ═O substituent.

“Thioxo” refers to the ═S substituent.

“Alkyl” refers to a straight or branched hydrocarbon chain radicalconsisting solely of carbon and hydrogen atoms, which is saturated orunsaturated (i.e., contains one or more double and/or triple bonds),having from one to twelve carbon atoms (C₁₋₁₂ alkyl), preferably one toeight carbon atoms (C₁-C₈ alkyl) or one to six carbon atoms (C₁-C₆alkyl), and which is attached to the rest of the molecule by a singlebond, e.g., methyl, ethyl, n-propyl, 1-methylethyl(iso-propyl), n-butyl,n-pentyl, 1,1-dimethylethyl(t-butyl), 3-methylhexyl, 2-methylhexyl,ethenyl, prop-1-enyl, but-1-enyl, pent-1-enyl, penta-1,4-dienyl,ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like. Unlessstated otherwise specifically in the specification, an alkyl group maybe optionally substituted.

“Alkylene” or “alkylene chain” refers to a straight or branched divalenthydrocarbon chain linking the rest of the molecule to a radical group,consisting solely of carbon and hydrogen, which is saturated orunsaturated (i.e., contains one or more double and/or triple bonds), andhaving from one to twelve carbon atoms, e.g., methylene, ethylene,propylene, n-butylene, ethenylene, propenylene, n-butenylene,propynylene, n-butynylene, and the like. The alkylene chain is attachedto the rest of the molecule through a single or double bond and to theradical group through a single or double bond. The points of attachmentof the alkylene chain to the rest of the molecule and to the radicalgroup can be through one carbon or any two carbons within the chain.Unless stated otherwise specifically in the specification, an alkylenechain may be optionally substituted.

“Alkoxy” refers to a radical of the formula —OR_(a) where R_(a) is analkyl radical as defined above containing one to twelve carbon atoms.Unless stated otherwise specifically in the specification, an alkoxygroup may be optionally substituted.

“Alkylamino” refers to a radical of the formula —NHR_(a) or —NR_(a)R_(a)where each R_(a) is, independently, an alkyl radical as defined abovecontaining one to twelve carbon atoms. Unless stated otherwisespecifically in the specification, an alkylamino group may be optionallysubstituted.

“Thioalkyl” refers to a radical of the formula —SR_(a) where R_(a) is analkyl radical as defined above containing one to twelve carbon atoms.Unless stated otherwise specifically in the specification, a thioalkylgroup may be optionally substituted.

“Aryl” refers to a hydrocarbon ring system radical comprising hydrogen,6 to 18 carbon atoms and at least one aromatic ring. For purposes ofthis invention, the aryl radical may be a monocyclic, bicyclic,tricyclic or tetracyclic ring system, which may include fused or bridgedring systems. Aryl radicals include, but are not limited to, arylradicals derived from aceanthrylene, acenaphthylene, acephenanthrylene,anthracene, azulene, benzene, chrysene, fluoranthene, fluorene,as-indacene, s-indacene, indane, indene, naphthalene, phenalene,phenanthrene, pleiadene, pyrene, and triphenylene. Unless statedotherwise specifically in the specification, the term “aryl” or theprefix “ar-” (such as in “aralkyl”) is meant to include aryl radicalsthat are optionally substituted.

“Aralkyl” refers to a radical of the formula —R_(b)—R_(e) where R_(b) isan alkylene chain as defined above and R_(e) is one or more arylradicals as defined above, for example, benzyl, diphenylmethyl and thelike. Unless stated otherwise specifically in the specification, anaralkyl group may be optionally substituted.

“Cycloalkyl” or “carbocyclic ring” refers to a stable non-aromaticmonocyclic or polycyclic hydrocarbon radical consisting solely of carbonand hydrogen atoms, which may include fused or bridged ring systems,having from three to fifteen carbon atoms, preferably having from threeto ten carbon atoms, and which is saturated or unsaturated and attachedto the rest of the molecule by a single bond. Monocyclic radicalsinclude, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl, and cyclooctyl. Polycyclic radicals include, for example,adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo[2.2.1]heptanyl,and the like. Unless otherwise stated specifically in the specification,a cycloalkyl group may be optionally substituted.

“Cycloalkylalkyl” refers to a radical of the formula —R_(b)R_(d) whereR_(d) is an alkylene chain as defined above and R_(g) is a cycloalkylradical as defined above. Unless stated otherwise specifically in thespecification, a cycloalkylalkyl group may be optionally substituted.

“Fused” refers to any ring structure described herein which is fused toan existing ring structure in the compounds of the invention. When thefused ring is a heterocyclyl ring or a heteroaryl ring, any carbon atomon the existing ring structure which becomes part of the fusedheterocyclyl ring or the fused heteroaryl ring may be replaced with anitrogen atom.

“Halo” or “halogen” refers to bromo, chloro, fluoro or iodo.

“Haloalkyl” refers to an alkyl radical, as defined above, that issubstituted by one or more halo radicals, as defined above, e.g.,trifluoromethyl, difluoromethyl, trichloromethyl, 2,2,2-trifluoroethyl,1,2-difluoroethyl, 3-bromo-2-fluoropropyl, 1,2-dibromoethyl, and thelike. Unless stated otherwise specifically in the specification, ahaloalkyl group may be optionally substituted.

“Heterocyclyl” or “heterocyclic ring” refers to a stable 3- to18-membered non-aromatic ring radical which consists of two to twelvecarbon atoms and from one to six heteroatoms selected from the groupconsisting of nitrogen, oxygen and sulfur. Unless stated otherwisespecifically in the specification, the heterocyclyl radical may be amonocyclic, bicyclic, tricyclic or tetracyclic ring system, which mayinclude fused or bridged ring systems; and the nitrogen, carbon orsulfur atoms in the heterocyclyl radical may be optionally oxidized; thenitrogen atom may be optionally quaternized; and the heterocyclylradical may be partially or fully saturated. Examples of suchheterocyclyl radicals include, but are not limited to, dioxolanyl,thienyl[1,3]dithianyl, decahydroisoquinolyl, imidazolinyl,imidazolidinyl, isothiazolidinyl, isoxazolidinyl, morpholinyl,octahydroindolyl, octahydroisoindolyl, 2-oxopiperazinyl,2-oxopiperidinyl, 2-oxopyrrolidinyl, oxazolidinyl, piperidinyl,piperazinyl, 4-piperidonyl, pyrrolidinyl, pyrazolidinyl, quinuclidinyl,thiazolidinyl, tetrahydrofuryl, trithianyl, tetrahydropyranyl,thiomorpholinyl, thiamorpholinyl, 1-oxo-thiomorpholinyl, and1,1-dioxo-thiomorpholinyl. Unless stated otherwise specifically in thespecification, Unless stated otherwise specifically in thespecification, a heterocyclyl group may be optionally substituted.

“N-heterocyclyl” refers to a heterocyclyl radical as defined abovecontaining at least one nitrogen and where the point of attachment ofthe heterocyclyl radical to the rest of the molecule is through anitrogen atom in the heterocyclyl radical. Unless stated otherwisespecifically in the specification, a N-heterocyclyl group may beoptionally substituted.

“Heterocyclylalkyl” refers to a radical of the formula —R_(b)R_(e) whereR_(b) is an alkylene chain as defined above and R_(e) is a heterocyclylradical as defined above, and if the heterocyclyl is anitrogen-containing heterocyclyl, the heterocyclyl may be attached tothe alkyl radical at the nitrogen atom. Unless stated otherwisespecifically in the specification, a heterocyclylalkyl group may beoptionally substituted.

“Heteroaryl” refers to a 5- to 14-membered ring system radicalcomprising hydrogen atoms, one to thirteen carbon atoms, one to sixheteroatoms selected from the group consisting of nitrogen, oxygen andsulfur, and at least one aromatic ring. For purposes of this invention,the heteroaryl radical may be a monocyclic, bicyclic, tricyclic ortetracyclic ring system, which may include fused or bridged ringsystems; and the nitrogen, carbon or sulfur atoms in the heteroarylradical may be optionally oxidized; the nitrogen atom may be optionallyquaternized. Examples include, but are not limited to, azepinyl,acridinyl, benzimidazolyl, benzothiazolyl, benzindolyl, benzodioxolyl,benzofuranyl, benzooxazolyl, benzothiazolyl, benzothiadiazolyl,benzo[b][1,4]dioxepinyl, 1,4-benzodioxanyl, benzonaphthofuranyl,benzoxazolyl, benzodioxolyl, benzodioxinyl, benzopyranyl,benzopyranonyl, benzofuranyl, benzofuranonyl,benzothienyl(benzothiophenyl), benzotriazolyl,benzo[4,6]imidazo[1,2-a]pyridinyl, carbazolyl, cinnolinyl,dibenzofuranyl, dibenzothiophenyl, furanyl, furanonyl, isothiazolyl,imidazolyl, indazolyl, indolyl, indazolyl, isoindolyl, indolinyl,isoindolinyl, isoquinolyl, indolizinyl, isoxazolyl, naphthyridinyl,oxadiazolyl, 2-oxoazepinyl, oxazolyl, oxiranyl, 1-oxidopyridinyl,1-oxidopyrimidinyl, 1-oxidopyrazinyl, 1-oxidopyridazinyl,1-phenyl-1H-pyrrolyl, phenazinyl, phenothiazinyl, phenoxazinyl,phthalazinyl, pteridinyl, purinyl, pyrrolyl, pyrazolyl, pyridinyl,pyrazinyl, pyrimidinyl, pyridazinyl, quinazolinyl, quinoxalinyl,quinolinyl, quinuclidinyl, isoquinolinyl, tetrahydroquinolinyl,thiazolyl, thiadiazolyl, triazolyl, tetrazolyl, triazinyl, andthiophenyl (i.e., thienyl). Unless stated otherwise specifically in thespecification, a heteroaryl group may be optionally substituted.

“N-heteroaryl” refers to a heteroaryl radical as defined abovecontaining at least one nitrogen and where the point of attachment ofthe heteroaryl radical to the rest of the molecule is through a nitrogenatom in the heteroaryl radical. Unless stated otherwise specifically inthe specification, an N-heteroaryl group may be optionally substituted.

“Heteroarylalkyl” refers to a radical of the formula —R_(b)R_(f) whereR_(b) is an alkylene chain as defined above and R_(f) is a heteroarylradical as defined above. Unless stated otherwise specifically in thespecification, a heteroarylalkyl group may be optionally substituted.

The term “substituted” used herein means any of the above groups (i.e.,alkyl, alkylene, alkoxy, alkylamino, thioalkyl, aryl, aralkyl,cycloalkyl, cycloalkylalkyl, haloalkyl, heterocyclyl, N-heterocyclyl,heterocyclylalkyl, heteroaryl, N-heteroaryl and/or heteroarylalkyl)wherein at least one hydrogen atom is replaced by a bond to anon-hydrogen atoms such as, but not limited to: a halogen atom such asF, Cl, Br, and I; an oxygen atom in groups such as hydroxyl groups,alkoxy groups, and ester groups; a sulfur atom in groups such as thiolgroups, thioalkyl groups, sulfone groups, sulfonyl groups, and sulfoxidegroups; a nitrogen atom in groups such as amines, amides, alkylamines,dialkylamines, arylamines, alkylarylamines, diarylamines, N-oxides,imides, and enamines; a silicon atom in groups such as trialkylsilylgroups, dialkylarylsilyl groups, alkyldiarylsilyl groups, andtriarylsilyl groups; and other heteroatoms in various other groups.“Substituted” also means any of the above groups in which one or morehydrogen atoms are replaced by a higher-order bond (e.g., a double- ortriple-bond) to a heteroatom such as oxygen in oxo, carbonyl, carboxyl,and ester groups; and nitrogen in groups such as imines, oximes,hydrazones, and nitriles. For example, “substituted” includes any of theabove groups in which one or more hydrogen atoms are replaced with—NR_(g)R_(h), —NR_(g)C(═O)R_(h), —NR_(g)C(═O)NR_(g)R_(h),—NR_(g)C(═O)OR_(h), —NR_(g)SO₂R_(h), OC(═O)NR_(g)R_(h), —OR_(g), SR_(g),—SOR_(B), —SO₂R_(g), —OSO₂R_(g), —SO₂OR_(g), ═NSO₂R_(g), and—SO₂NR_(g)R_(h). “Substituted” also means any of the above groups inwhich one or more hydrogen atoms are replaced with —C(═O)R_(g),—C(═O)OR_(g), —C(═O)NR_(g)R_(h), —CH₂SO₂R_(g), —CH₂SO₂NR_(g)R_(h),—(CH₂CH₂O)₂₋₁₀R_(g). In the foregoing, R_(g) and R_(h) are the same ordifferent and independently hydrogen, alkyl, alkoxy, alkylamino,thioalkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, haloalkyl,heterocyclyl, N-heterocyclyl, heterocyclylalkyl, heteroaryl,N-heteroaryl and/or heteroarylalkyl. “Substituted” further means any ofthe above groups in which one or more hydrogen atoms are replaced by abond to an amino, cyano, hydroxyl, imino, nitro, oxo, thioxo, halo,alkyl, alkoxy, alkylamino, thioalkyl, aryl, aralkyl, cycloalkyl,cycloalkylalkyl, haloalkyl, heterocyclyl, N-heterocyclyl,heterocyclylalkyl, heteroaryl, N-heteroaryl and/or heteroarylalkylgroup. The above non-hydrogen groups are generally referred to herein as“substituents”. In addition, each of the foregoing substituents may alsobe optionally substituted with one or more of the above substituents.

“Prodrug” is meant to indicate a compound that may be converted underphysiological conditions or by solvolysis to a biologically activecompound of the invention. Thus, the term “prodrug” refers to ametabolic precursor of a compound of the invention that ispharmaceutically acceptable. A prodrug may be inactive when administeredto a subject in need thereof, but is converted in vivo to an activecompound of the invention. Prodrugs are typically rapidly transformed invivo to yield the parent compound of the invention, for example, byhydrolysis in blood. The prodrug compound often offers advantages ofsolubility, tissue compatibility or delayed release in a mammalianorganism (see, Bundgard, H., Design of Prodrugs (1985), pp. 7-9, 21-24(Elsevier, Amsterdam)). A discussion of prodrugs is provided in Higuchi,T., et al., A.C.S. Symposium Series, Vol. 14, and in BioreversibleCarriers in Drug Design, Ed. Edward B. Roche, American PharmaceuticalAssociation and Pergamon Press, 1987.

The term “prodrug” is also meant to include any covalently bondedcarriers, which release the active compound of the invention in vivowhen such prodrug is administered to a mammalian subject. Prodrugs of acompound of the invention may be prepared by modifying functional groupspresent in the compound of the invention in such a way that themodifications are cleaved, either in routine manipulation or in vivo, tothe parent compound of the invention. Prodrugs include compounds of theinvention wherein a hydroxy, amino or mercapto group is bonded to anygroup that, when the prodrug of the compound of the invention isadministered to a mammalian subject, cleaves to form a free hydroxy,free amino or free mercapto group, respectively. Examples of prodrugsinclude, but are not limited to, acetate, formate and benzoatederivatives of alcohol or amide derivatives of amine functional groupsin the compounds of the invention and the like.

The invention disclosed herein is also meant to encompass the in vivometabolic products of the disclosed compounds. Such products may resultfrom, for example, the oxidation, reduction, hydrolysis, amidation,esterification, and the like of the administered compound, primarily dueto enzymatic processes. Accordingly, the invention includes compoundsproduced by a process comprising administering a compound of thisinvention to a mammal for a period of time sufficient to yield ametabolic product thereof. Such products are typically identified byadministering a radiolabelled compound of the invention in a detectabledose to an animal, such as rat, mouse, guinea pig, monkey, or to human,allowing sufficient time for metabolism to occur, and isolating itsconversion products from the urine, blood or other biological samples.

“Stable compound” and “stable structure” are meant to indicate acompound that is sufficiently robust to survive isolation to a usefuldegree of purity from a reaction mixture, and formulation into anefficacious therapeutic agent.

“Mammal” includes humans and both domestic animals such as laboratoryanimals and household pets (e.g., cats, dogs, swine, cattle, sheep,goats, horses, rabbits), and non-domestic animals such as wildlife andthe like.

“Optional” or “optionally” means that the subsequently described eventor circumstances may or may not occur, and that the description includesinstances where said event or circumstance occurs and instances in whichit does not. For example, “optionally substituted aryl” means that thearyl radical may or may not be substituted and that the descriptionincludes both substituted aryl radicals and aryl radicals having nosubstitution.

“Pharmaceutically acceptable carrier, diluent or excipient” includeswithout limitation any adjuvant, carrier, excipient, glidant, sweeteningagent, diluent, preservative, dye/colorant, flavor enhancer, surfactant,wetting agent, dispersing agent, suspending agent, stabilizer, isotonicagent, solvent, or emulsifier which has been approved by the UnitedStates Food and Drug Administration as being acceptable for use inhumans or domestic animals.

“Pharmaceutically acceptable salt” includes both acid and base additionsalts.

“Pharmaceutically acceptable acid addition salt” refers to those saltswhich retain the biological effectiveness and properties of the freebases, which are not biologically or otherwise undesirable, and whichare formed with inorganic acids such as, but are not limited to,hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,phosphoric acid and the like, and organic acids such as, but not limitedto, acetic acid, 2,2-dichloroacetic acid, adipic acid, alginic acid,ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid,4-acetamidobenzoic acid, camphoric acid, camphor-10-sulfonic acid,capric acid, caproic acid, caprylic acid, carbonic acid, cinnamic acid,citric acid, cyclamic acid, dodecylsulfuric acid, ethane-1,2-disulfonicacid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, formic acid,fumaric acid, galactaric acid, gentisic acid, glucoheptonic acid,gluconic acid, glucuronic acid, glutamic acid, glutaric acid,2-oxo-glutaric acid, glycerophosphoric acid, glycolic acid, hippuricacid, isobutyric acid, lactic acid, lactobionic acid, lauric acid,maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonicacid, mucic acid, naphthalene-1,5-disulfonic acid,naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid,oleic acid, orotic acid, oxalic acid, palmitic acid, pamoic acid,propionic acid, pyroglutamic acid, pyruvic acid, salicylic acid,4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid,tartaric acid, thiocyanic acid, p-toluenesulfonic acid, trifluoroaceticacid, undecylenic acid, and the like.

“Pharmaceutically acceptable base addition salt” refers to those saltswhich retain the biological effectiveness and properties of the freeacids, which are not biologically or otherwise undesirable. These saltsare prepared from addition of an inorganic base or an organic base tothe free acid. Salts derived from inorganic bases include, but are notlimited to, the sodium, potassium, lithium, ammonium, calcium,magnesium, iron, zinc, copper, manganese, aluminum salts and the like.Preferred inorganic salts are the ammonium, sodium, potassium, calcium,and magnesium salts. Salts derived from organic bases include, but arenot limited to, salts of primary, secondary, and tertiary amines,substituted amines including naturally occurring substituted amines,cyclic amines and basic ion exchange resins, such as ammonia,isopropylamine, trimethylamine, diethylamine, triethylamine,tripropylamine, diethanolamine, ethanolamine, deanol,2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine,lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline,betaine, benethamine, benzathine, ethylenediamine, glucosamine,methylglucamine, theobromine, triethanolamine, tromethamine, purines,piperazine, piperidine, N-ethylpiperidine, polyamine resins and thelike. Particularly preferred organic bases are isopropylamine,diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, cholineand caffeine.

Often crystallizations produce a solvate of the compound of theinvention. As used herein, the term “solvate” refers to an aggregatethat comprises one or more molecules of a compound of the invention withone or more molecules of solvent. The solvent may be water, in whichcase the solvate may be a hydrate. Alternatively, the solvent may be anorganic solvent. Thus, the compounds of the present invention may existas a hydrate, including a monohydrate, dihydrate, hemihydrate,sesquihydrate, trihydrate, tetrahydrate and the like, as well as thecorresponding solvated fauns. The compound of the invention may be truesolvates, while in other cases, the compound of the invention may merelyretain adventitious water or be a mixture of water plus someadventitious solvent.

A “pharmaceutical composition” refers to a formulation of a compound ofthe invention and a medium generally accepted in the art for thedelivery of the biologically active compound to mammals, e.g., humans.Such a medium includes all pharmaceutically acceptable carriers,diluents or excipients therefor.

“Effective amount” or “therapeutically effective amount” refers to thatamount of a compound of the invention which, when administered to amammal, preferably a human, is sufficient to inhibit phosphatetransport, inhibit sodium-mediated phosphate uptake, reduce serum PTH,calcium, calcitriol, and phosphate concentrations or levels, treat renaldisease or treat hyperphosphatemia in the mammal, preferably a human.The amount of a compound of the invention which constitutes a“therapeutically effective amount” will vary depending on the compound,the condition and its severity, the manner of administration, and theage of the mammal to be treated, but can be determined routinely by oneof ordinary skill in the art having regard to his own knowledge and tothis disclosure.

“Treating” or “treatment” as used herein covers the treatment of thedisease or condition of interest in a mammal, preferably a human, havingthe disease or condition of interest, and includes:

(i) preventing the disease or condition from occurring in a mammal, inparticular, when such mammal is predisposed to the condition but has notyet been diagnosed as having it;

(ii) inhibiting the disease or condition, i.e., arresting itsdevelopment;

(iii) relieving the disease or condition, i.e., causing regression ofthe disease or condition; or

(iv) relieving the symptoms resulting from the disease or condition,i.e., relieving pain without addressing the underlying disease orcondition. As used herein, the terms “disease” and “condition” may beused interchangeably or may be different in that the particular maladyor condition may not have a known causative agent (so that etiology hasnot yet been worked out) and it is therefore not yet recognized as adisease but only as an undesirable condition or syndrome, wherein a moreor less specific set of symptoms have been identified by clinicians.

The compounds of the invention, or their pharmaceutically acceptablesalts may contain one or more asymmetric centers and may thus give riseto enantiomers, diastereomers, and other stereoisomeric forms that maybe defined, in terms of absolute stereochemistry, as (R)- or (S)- or, as(D)- or (L)- for amino acids. The present invention is meant to includeall such possible isomers, as well as their racemic and optically pureforms. Optically active (+) and (−), (R)- and (S)-, or (D)- and(L)-isomers may be prepared using chiral synthons or chiral reagents, orresolved using conventional techniques, for example, chromatography andfractional crystallization. Conventional techniques for thepreparation/isolation of individual enantiomers include chiral synthesisfrom a suitable optically pure precursor or resolution of the racemate(or the racemate of a salt or derivative) using, for example, chiralhigh pressure liquid chromatography (HPLC). When the compounds describedherein contain olefinic double bonds or other centres of geometricasymmetry, and unless specified otherwise, it is intended that thecompounds include both E and Z geometric isomers. Likewise, alltautomeric forms are also intended to be included.

A “stereoisomer” refers to a compound made up of the same atoms bondedby the same bonds but having different three-dimensional structures,which are not interchangeable. The present invention contemplatesvarious stereoisomers and mixtures thereof and includes “enantiomers”,which refers to two stereoisomers whose molecules are nonsuperimposeablemirror images of one another.

A “tautomer” refers to a proton shift from one atom of a molecule toanother atom of the same molecule. The present invention includestautomers of any said compounds.

As noted above, in one embodiment of the present invention, compoundshaving activity as phosphate transport inhibitors, more specifically,inhibitors of intestinal apical membrane Na/phosphate co-transport, areprovided, the compounds having the following structure (I):

or a stereoisomer, prodrug or pharmaceutically acceptable salt thereof,

wherein:

-   -   X is substituted aryl or substituted heteroaryl;    -   Y is halogen, optionally substituted alkylamino, optionally        substituted alkoxy, optionally substituted thioalkyl, optionally        substituted cycloalkyl, optionally substituted heterocyclyl,        optionally substituted aryl, —O(optionally substituted        cycloalkyl), —O(optionally substituted heterocyclyl) or        —O(optionally substituted aryl);    -   each R₁ is, independently, hydrogen, halogen, C₁₋₆alkyl or        C₁₋₆haloalkyl; and    -   R₂ is hydrogen or optionally substituted C₁₋₆alkyl.

In further embodiments, Y is halogen, such as chloro.

In other further embodiments, Y is alkylamino, such as diethylamino.

In other further embodiments, Y is alkoxy.

In other further embodiments, Y is heterocyclyl, such as 1-piperidinyland the compound has the structure:

In other further embodiments, Y is —O(cycloalkyl).

In other further embodiments, X is —ZR₃, where Z is aryl or heteroaryland R₃ represents a non-hydrogen substituent as defined above, or asmore specifically defined below.

In more specific embodiments, Z is aryl, such as phenyl and the compoundhas the structure:

In other more specific embodiments, Z is heteroaryl, such as pyridinyland the compound has the structure:

In more specific embodiments of the foregoing, R₃ is:

-   -   (a) —CH₂S(O)₀₋₂(optionally substituted C₁₋₆alkyl)C(═O)NR₇R₄,    -   (b) —CH₂S(O)₀₋₂(optionally substituted C₁₋₆alkyl)NR₇R₄,    -   (c) —CH₂S(O)₀₋₂(optionally substituted C₁₋₆alkyl)C(═O)OR₅,    -   (d) —CH₂S(O)₀₋₂(optionally substituted C₁₋₆alkyl)OR₅,    -   (e) —CH₂S(O)₀₋₂(optionally substituted C₁₋₆alkyl)R₆,    -   (f) —CH₂S(O)₀₋₂R₆,    -   (g) —CH₂S(O)₀₋₂NR₇R₄,    -   (h) —CH₂S(O)₀₋₂(CH₂CH₂O)_(x)R₅,    -   (i) —CH₂NR₇(CH₂CH₂O)_(x)R₅,    -   (j) —C(═O)NR₇(optionally substituted C₁₋₆alkyl)C(═O)NR₇R₄,    -   (k) —C(═O)NR₇(optionally substituted C₁₋₆alkyl)NR₇R₄,    -   (l) —C(═O)NR₇(optionally substituted C₁₋₆alkyl)C(═O)OR₅,    -   (m) —C(═O)NR₇(optionally substituted C₁₋₆alkyl)OR₅,    -   (n)—C(═O)NR₇(optionally substituted C₁₋₆alkyl)R₆, or    -   (o) —C(═O)NR₇(CH₂CH₂O)_(x)R₅;

wherein

-   -   R₄ is hydrogen, hydroxyl, alkoxy, optionally substituted        C₁₋₆alkyl, optionally substituted aryl, optionally substituted        heterocyclyl or optionally substituted heteroaryl;    -   R₅ is hydrogen, optionally substituted C₁₋₆alkyl, optionally        substituted aryl, optionally substituted heterocyclyl or        optionally substituted heteroaryl;    -   R₆ is optionally substituted aryl, optionally substituted        heterocyclyl or optionally substituted heteroaryl;    -   R₇ is hydrogen or optionally substituted C₁₋₆alkyl; and    -   x is an integer from 2 to 10.

In other further embodiments, each R₁ is hydrogen.

In other further embodiments, R₂ is hydrogen.

In other further embodiments, R₂ is an optionally substituted C₁₋₆alkyl,such as trifluoromethyl.

It is understood that any embodiment of the compounds of structure (I),as set forth above, and any specific substituent set forth herein for aX, Y, R₁, R₂, R₃, R₄, R₅, R₆ or R₇ group in the compounds of structure(I), as set forth above, may be independently combined with otherembodiments and/or substituents of compounds of structure (I) to formembodiments of the inventions not specifically set forth above. Inaddition, in the event that a list of substitutents is listed for anyparticular substituent in a particular embodiment and/or claim, it isunderstood that each individual substituent may be deleted from theparticular embodment and/or claim and that the remaining list ofsubstituents will be considered to be within the scope of the invention.

In accordance with the present disclosure, it has been discovered thatphosphate absorption from the intestine in patients with elevatedphosphate serum levels may be limited, and preferably substantiallyprevented, through inhibition of the intestinal transport system whichmediates phosphate uptake in the intestine. This inhibition may beachieved by the administration of certain compounds, and/orpharmaceutical compositions comprising them, which may advantageously bedesigned such that little, or substantially none, of the compound isabsorbed into the blood stream (that is, it is designed to benon-systemic or substantially non-systemic). Such compounds aredescribed as generally abiding by “Ardelyx Rules.” In this regard, thecompounds have features that give rise to little or substantially nosystemic availability. In other words, the compounds are not absorbedinto the bloodstream at meaningful levels and therefore have no activitythere, but instead have their activity localized substantially withinthe GI tract.

Therefore, in certain illustrative embodiments as further describedherein, the compounds of the invention generally require a combinationof structural and/or functional features relating or contributing totheir activity in the GI tract and/or their substantial non-systemicbioavailability. Such features may include, for example, one or more of(i) specific tPSA and/or MW values (e.g., at least about 190 Å² and/orat least about 736 Daltons, respectively), (ii) specific levels of fecalrecovery of the compound and/or its metabolites after administration(e.g., greater than 50% at 72 hours); (iii) specific numbers of NHand/or OH and/or potentially hydrogen bond donor moieties (e.g., greaterthan about five); (iv) specific numbers of rotatable bonds (e.g.,greater than about five); (iv) specific permeability features (e.g.,P_(app) less than about 100×10⁻⁶ cm/s); and/or any of a number of otherfeatures and characteristics as described herein.

The compounds of the present invention offer numerous advantages in thetreatment of GI tract and other disorders. For example, the compoundsare active on the phosphate transporter apically located in theintestine and essentially do not reach other phosphate transportersexpressed in other tissues and organs. For instance the NaPi2btransporter is primarily expressed in the apical membrane of intestinalenterocytes, but is also found in salivary glands, mammary glands, lung,kidney, pancreas, ovary, prostate, testis and liver (Feild et al., 1999,Biochem Biophys Res Commun, v. 258, no. 3, p. 578-582; Bai et al., 2000,Am J Physiol Cell Physiol, v. 279, no. 4, p. C1135-C1143; Virkki et al.,2007, Am J Physiol Renal Physiol, v. 293, no. 3, p. F643-F654). Genomewide single-nucleotide polymorphism analysis in patients with pulmonaryalveolar microlithiasis (PAM) has revealed a link between a mutatedNaPi2b gene and disorder in which microliths are formed in the lungalveolar space. Homozygous inactivating mutations of pulmonary NaPi2bhave also been implicated in the pathophysiology of PAM (Huqun et al.,2007, Am J Respir Crit. Care Med, v. 175, no. 3, p. 263-268). Consistentwith this human study, calcification nodules were evident in NaPi2bconditional knockout mice but not in wild type animals after NaPi2bdeletion. In contrast, analysis of kidney and ileum samples revealed nopathologic abnormalities associated with Npt2b deletion (Sabbagh et al.,2009, J Am Soc. Nephrol., 20: 2348-2358).

The essentially non-systemic NaPi2b inhibitors of the present inventiondo not interfere with the pulmonary function of NaPi2b and, therefore,potential pulmonary toxicity is minimized. In addition, certain patientpopulations to whom the compounds of the invention may be administeredare expected to have limited kidney clearance rate secondary to adeclining kidney function. Thus, systemic compounds with some kidneyclearance contribution in their excretion pathway can accumulate in theplasma, potentially leading to undesired side-effects in those patientswith chronic kidney disease (Sica, 2008, J Clin Hypertens. (Greenwich.),v. 10, no. 7, p. 541-548). The compounds of the invention do not giverise to these same concerns because of their limited systemicavailability.

As further detailed below, phosphate absorption in the upper intestineis mediated, at least in part, by a carrier-mediated mechanism whichcouples the absorption of phosphate to that of sodium. Accordingly,inhibition of intestinal phosphate transport will reduce body phosphorusoverload. In patients with advanced kidney disease (e.g. stage 4 and 5),the body phosphorus overload manifests itself by serum phosphateconcentration above normal levels, i.e. hyperphosphatemia.Hyperphosphatemia is directly related to mortality and morbidity.Inhibition of intestinal phosphate transport will reduce serum phosphateconcentration and therefore improve outcome in those patients. In stage2 and 3 chronic kidney disease patients, the body phosphorus overloaddoes not necessarily lead to hyperphosphatemia, i.e. patients remainnormophosphatemic, but there is a need to reduce body phosphorusoverload even at those early stages to avoid associated bone andvascular disorders, and ultimately improve mortality rate. Similarly,inhibition of intestinal phosphate transport will be particularlyadvantageous in patients that have a disease that is treatable byinhibiting the uptake of phosphate from the intestines. Inhibition ofphosphate absorption from the glomerular filtrate within the kidneyswould also be advantageous for treating chronic renal failure.Furthermore, inhibition of phosphate transport may slow the progressionof renal failure and reduce risk of cardiovascular events.

Without being held to any particular theory, it is generally believedthat, in vertebrates, phosphate (Pi) transporters use the inwardlydirected electrochemical gradient of Na+ ions, established by the Na/KATPase transporter, to drive Pi influx. These transporters fall in threedistinct and unrelated Pi transporters proteins named type I, II andIII. NaPi type I transporters comprise NaPi-I, mainly expressed in theproximal and distal renal tubules. NaPi type II transporters compriseNaPi2a, NaPi2b, and NaPi2c. NaPi2a is localized in the apical membraneof proximal renal tubule, but is also detected in rat brain, osteoclastsand osteoblast-like cells. NaPi2b is expressed in the apical membrane ofenterocytes, but also found in lung, colon, testis and liver (see, e.g.,Virkki, L. V., et al., Phosphate Transporters: A Tale of Two SoluteCarrier Families, Am. J. Physiol. Renal. Physiol., 293(3):F643-54(2007)). Type III NaPi transporters comprise PiT-1 and PiT-2, which arenow emerging as important players in bone Pi metabolism and vascularcalcification.

NaPi2a is believed to play a key role in phosphorus homeostasis bycontrolling the reabsorption of Pi in the renal proximal tubule. This isexemplified in NaPi2a KO mice, which develop hyperphosphaturia andhypophosphatemia. NaPi2b is believed responsible for transepithelialabsorption in the small intestine and is regulated by dietary Pi andvitamin D (Calcitriol (1,25-Dihydroxycholecalciferol)). NaPi2c isexpressed in renal tubule and other tissues (see, e.g., Virkki, L. V.,et al., Id.).

The basic transport mechanism of NaPi2a and NaPi2b is the same (see,e.g., Murer, H., et al., Proximal Tubular Phosphate Reabsorption:Molecular Mechanisms, Physiol. Rev., 80(4):1373-409 (2000)); both areelectrogenic with a stoichiometry of about 3:1 Na⁺:HPO₄ ²⁻, meaning that3 Na⁺ are co-transported with one phosphate anion. The additional Nacations translocated are excreted on the basolateral membrane via theK/Na ATPase active transporters to preserve cell polarization. Renal Pitransporter NaPi2a activity is increased in the kidney in response tolow dietary Pi (see, e.g., Murer, et al., Id.). This results from anincrease in transporter expression on the apical membrane of the kidneytubule. Histochemical analysis suggests a “recruitment” phenomenon. Itis to be noted that, in contrast, the type I Na-Pi transporter does notrespond to change in dietary P. The change in NaPi2a expression isparalleled by alteration in parathyroid hormone PTH plasma concentrationand vice-versa (e.g., injection of PTH in rats leads within minutes to areduction in brush border membrane transporter content). Acid-basechange can also alter expression of NaPi2a. Chronic metabolic acidosisin rats significantly decreases NaPi2a protein and mRNA content. Thesame is observed in CKD rats induced by ⅚^(th) nephrectomy. Theregulation of apical NaPi2a transporters involves complex membraneretrieval and re-insertion mechanisms. Control in transport activity canalso be controlled by changes in intra-tubular and intracellular pH, intransmembrane potential difference and posttranslational modification.

Substantially Impermeable or Substantially Systemically Non-BioavailablePhosphate Transport Inhibitor Compounds

A. Physical and Performance Properties

In accordance with the present disclosure, the compounds describedherein are designed to be substantially active or localized in thegastrointestinal lumen of a human or animal subject. The term“gastrointestinal lumen” is used interchangeably herein with the term“lumen,” to refer to the space or cavity within a gastrointestinal tract(GI tract, which can also be referred to as the gut), delimited by theapical membrane of GI epithelial cells of the subject. In someembodiments, the compounds are not absorbed through the layer ofepithelial cells of the GI tract (also known as the GI epithelium).“Gastrointestinal mucosa” refers to the layer(s) of cells separating thegastrointestinal lumen from the rest of the body and includes gastricand intestinal mucosa, such as the mucosa of the small intestine. A“gastrointestinal epithelial cell” or a “gut epithelial cell” as usedherein refers to any epithelial cell on the surface of thegastrointestinal mucosa that faces the lumen of the gastrointestinaltract, including, for example, an epithelial cell of the stomach, anintestinal epithelial cell, a colonic epithelial cell, and the like.

“Substantially systemically non-bioavailable” and/or “substantiallyimpermeable” as used herein (as well as variations thereof) generallyrefer to situations in which a statistically significant amount, and insome embodiments essentially all of the compound of the presentdisclosure, remains in the gastrointestinal lumen. For example, inaccordance with one or more embodiments of the present disclosure,preferably at least about 70%, about 80%, about 90%, about 95%, about98%, about 99%, or even about 99.5%, of the compound remains in thegastrointestinal lumen. In such cases, localization to thegastrointestinal lumen refers to reducing net movement across agastrointestinal layer of epithelial cells, for example, by way of bothtranscellular and paracellular transport, as well as by active and/orpassive transport. The compound in such embodiments is hindered from netpermeation of a layer of gastrointestinal epithelial cells intranscellular transport, for example, through an apical membrane of anepithelial cell of the small intestine. The compound in theseembodiments is also hindered from net permeation through the “tightjunctions” in paracellular transport between gastrointestinal epithelialcells lining the lumen.

In this regard it is to be noted that, in one particular embodiment, thecompound is essentially not absorbed at all by the GI tract orgastrointestinal lumen. As used herein, the terms “substantiallyimpermeable” or “substantially systemically non-bioavailable” refers toembodiments wherein no detectable amount of absorption or permeation orsystemic exposure of the compound is detected, using means generallyknown in the art.

In this regard it is to be further noted, however, that in alternativeembodiments “substantially impermeable” or “substantially systemicallynon-bioavailable” provides or allows for some limited absorption in theGI tract, and more particularly the gut epithelium, to occur (e.g., somedetectable amount of absorption, such as for example at least about0.1%, 0.5%, 1% or more and less than about 30%, 20%, 10%, 5%, etc., therange of absorption being for example between about 1% and 30%, or 5%and 20%, etc.); stated another way, “substantially impermeable” or“substantially systemically non-bioavailable” refers to compounds thatexhibit some detectable permeability to an epithelial layer of cells inthe GI tract of less than about 20% of the administered compound (e.g.,less than about 15%, about 10%, or even about 5%, and for examplegreater than about 0.5%, or 1%), but then are cleared by the liver(i.e., hepatic extraction) and/or the kidney (i.e., renal excretion).

In this regard it is to be further noted, that in certain embodiments,due to the substantial impermeability and/or substantial systemicnon-bioavailability of the compounds of the present invention, greaterthan about 50%, 60%, 70%, 80% or 90% of a compound of the invention isrecoverable from the feces over, for example, a 24, 48 or 72 hour periodfollowing administration to a patient in need thereof. In this respect,it is understood that a recovered compound can include the sum of theparent compound and its metabolites derived from the parent compound,e.g., by means of hydrolysis, conjugation, reduction, oxidation,N-alkylation, glucuronidation, acetylation, methylation, sulfation,phosphorylation, or any other modification that adds atoms to or removesatoms from the parent compound, wherein the metabolites are generatedvia the action of any enzyme or exposure to any physiologicalenvironment including, pH, temperature, pressure, or interactions withfoodstuffs as they exist in the digestive milieu. Measurement of fecalrecovery of compound and metabolites can be carried out using standardmethodology. For example, compound can be administered orally at asuitable dose (e.g., 10 mg/kg) and feces are then collected atpredetermined times after dosing (e.g., 24 hours, 48 hours, 72 hours).Parent compound and metabolites can be extracted with organic solventand analyzed quantitatively using mass spectrometry. A mass balanceanalysis of the parent compound and metabolites (including, parent=M,metabolite 1 [M+16], and metabolite 2 [M+32]) can be used to determinethe percent recovery in the feces.

In certain preferred embodiments, the phosphate transport inhibitors ofthe present invention are not competitive inhibitors with respect tophosphate of Na/phosphate co-transport. In certain other preferredembodiments, the phosphate transport inhibitors of the invention arenon-competitive inhibitors. Non-competitive inhibitors maintain theirdegree of inhibition irrespective of the local phosphate concentration.This feature is an important aspect in providing an efficient blockadeof intestinal transport in postprandial state, where the localconcentration of dietary phosphate can attain concentration as high as10 mM. It is believed that competitive inhibitors are too sensitive tolocal phosphate concentration and unable to block phosphate uptakefollowing a high phosphorus meal. Various methods are available fordetermining whether a phosphate transport inhibitor is non-competitiveor competitive.

For example, a phosphate uptake assay can be performed and the IC₅₀values for a compound at different phosphate concentrations can bedetermined (e.g., “Enzyme kinetics”, I. Segel, 1975, John-Wiley & Sons,p. 123). IC₅₀ values for non-competitive inhibitors will remain the sameor similar with respect to the phosphate concentration, whereas IC₅₀values for competitive inhibitors will increase (i.e lose potency) asphosphate concentration increases.

(i) Permeability

In this regard it is to be noted that, in various embodiments, theability of the compound to be substantially systemicallynon-bioavailable is based on the compound charge, size, and/or otherphysicochemical parameters (e.g., polar surface area, number of hydrogenbond donors and/or acceptors therein, number of freely rotatable bonds,etc.). More specifically, it is to be noted that the absorptioncharacter of a compound can be selected by applying principles ofpharmacokinetics, for example, by applying Lipinski's rule, also knownas “the rule of five.” Although not a rule, but rather a set ofguidelines, Lipinski shows that small molecule drugs with (i) amolecular weight, (ii) a number of hydrogen bond donors, (iii) a numberof hydrogen bond acceptors, and/or (iv) a water/octanol partitioncoefficient (Moriguchi Log P), greater than a certain threshold value,generally do not show significant systemic concentration (i.e., aregenerally not absorbed to any significant degree). (See, e.g., Lipinskiet al., Advanced Drug Delivery Reviews, 46, 2001 3-26, incorporatedherein by reference.) Accordingly, substantially systemicallynon-bioavailable compounds (e.g., substantially systemicallynon-bioavailable phosphate transport inhibitor compounds) can bedesigned to have molecular structures exceeding one or more ofLipinski's threshold values. (See also Lipinski et al., Experimental andComputational Approaches to Estimate Solubility and Permeability in DrugDiscovery and Development Settings, Adv. Drug Delivery Reviews, 46:3-26(2001); and Lipinski, Drug-like Properties and the Causes of PoorSolubility and Poor Permeability, J. Pharm. & Toxicol. Methods,44:235-249 (2000), incorporated herein by reference.)

In some embodiments, for example, a substantially impermeable orsubstantially systemically non-bioavailable phosphate transportinhibitor compound of the present disclosure can be constructed tofeature one or more of the following characteristics: (i) a MW greaterthan about 500 Da, about 1000 Da, about 2500 Da, about 5000 Da, about10,000 Da or more (in the non-salt form of the compound); (ii) a totalnumber of NH and/or OH and/or other potential hydrogen bond donorsgreater than about 5, about 10, about 15 or more; (iii) a total numberof O atoms and/or N atoms and/or other potential hydrogen bond acceptorsgreater than about 5, about 10, about 15 or more; (iv) a Moriguchipartition coefficient greater than about 10⁵ (i.e., Log P greater thanabout 5, about 6, about 7, etc.), or alternatively less than about 10(i.e., a Log P of less than 1, or even 0); and/or (v) a total number ofrotatable bonds greater than about 5, about 10 or about 15, or more.

In addition to the parameters noted above, the molecular polar surfacearea (i.e., “PSA”), which may be characterized as the surface belongingto polar atoms, is a descriptor that has also been shown to correlatewell with passive transport through membranes and, therefore, allowsprediction of transport properties of drugs. It has been successfullyapplied for the prediction of intestinal absorption and Caco2 cellmonolayer penetration. (For Caco2 cell monolayer penetration testdetails, see for example the description of the Caco2 Model provided inExample 31 of U.S. Pat. No. 6,737,423, the entire contents of which areincorporated herein by reference, and the text of Example 31 inparticular, which may be applied for example to the evaluation ortesting of the compounds of the present disclosure.) PSA is expressed inÅ² (squared angstroms) and is computed from a three-dimensionalmolecular representation. A fast calculation method is also available(see, e.g., Ertl et al., Journal of Medicinal Chemistry, 2000, 43,3714-3717, the entire contents of which are incorporated herein byreference for all relevant and consistent purposes) using a desktopcomputer and commercially available chemical graphic tools packages,such as ChemDraw. The term “topological PSA” (tPSA) has been coined forthis fast-calculation method. tPSA is well correlated with humanabsorption data with common drugs (see, e.g., Table 1, below):

TABLE 1 name % FA^(a) TPSA^(b) metoprolol 102 50.7 nordiazepam 99 41.5diazepam 97 32.7 oxprenolol 97 50.7 phenazone 97 26.9 oxazepam 97 61.7alprenolol 96 41.9 practolol 95 70.6 pindolol 92 57.3 ciprofloxacin 6974.6 metolazone 64 92.5 tranexamic acid 55 63.3 atenolol 54 84.6sulpiride 36 101.7 mannitol 26 121.4 foscarnet 17 94.8 sulfasalazine 12141.3 olsalazine 2.3 139.8 lactulose 0.6 197.4 raffinose 0.3 268.7(from Ertl et al., J. Med. Chem., 2000, 43:3714-3717). Accordingly, insome embodiments, the compounds of the present disclosure may beconstructed to exhibit a tPSA value greater than about 100 Å², about 120Å², about 130 Å², or about 140 Å², and in some instances about 150 Å²,about 160 Å², about 170 Å², about 180 Å², about 190 Å², about 200 Å²,about 225 Å², about 250 Å², about 270 Å², about 300 Å², about 350 Å²,about 400 Å², about 450 Å², about 500 Å², about 750 Å², or even about1000 Å², such that the compounds are substantially impermeable orsubstantially systemically non-bioavailable (as defined elsewhereherein).

Because there are exceptions to Lipinski's “rule,” or the tPSA model,the permeability properties of the compounds of the present disclosuremay be screened experimentally. The permeability coefficient can bedetermined by methods known to those of skill in the art, including forexample by Caco-2 cell permeability assay and/or using an artificialmembrane as a model of a gastrointestinal epithelial cell. A syntheticmembrane impregnated with, for example, lecithin and/or dodecane tomimic the net permeability characteristics of a gastrointestinal mucosamay be utilized as a model of a gastrointestinal mucosa. The membranecan be used to separate a compartment containing the compound of thepresent disclosure from a compartment where the rate of permeation willbe monitored. Also, parallel artificial membrane permeability assays(PAMPA) can be performed. Such in vitro measurements can reasonablyindicate actual permeability in vivo. (See, for example, Wohnsland etal., J. Med. Chem., 2001, 44:923-930; Schmidt et al., Millipore Corp.Application Note, 2002, n° AN1725EN00, and n° AN1728EN00, incorporatedherein by reference.)

Accordingly, in some embodiments, the compounds utilized in the methodsof the present disclosure may have a permeability coefficient, P_(app),of less than about 100×10⁻⁶ cm/s, or less than about 10×10⁻⁶ cm/s, orless than about 1×10⁻⁶ cm/s, or less than about 0.1×10⁻⁶ cm/s, whenmeasured using means known in the art (such as for example thepermeability experiment described in Wohnsland et al., J. Med. Chem.,2001, 44. 923-930, the contents of which is incorporated herein byreference).

As previously noted, in accordance with the present disclosure,phosphate transport inhibitors may be modified to hinder their netabsorption through a layer of gut epithelial cells, rendering themsubstantially systemically non-bioavailable. In some particularembodiments, the compounds of the present disclosure comprise aphosphate transport inhibitor linked, coupled or otherwise attached to anon-absorbable moiety, which may be an oligomer moiety, a polymermoiety, a hydrophobic moiety, a hydrophilic moiety, and/or a chargedmoiety, which renders the overall compound substantially impermeable orsubstantially systemically non-bioavailable. In some preferredembodiments, the phosphate transport inhibitor is coupled to a multimeror polymer portion or moiety, such that the resulting molecule issubstantially impermeable or substantially systemicallynon-bioavailable. The multimer or polymer portion or moiety may be of amolecular weight greater than about 500 Daltons (Da), about 1000 Da,about 2500 Da, about 5000 Da, about 10,000 Da or more, and in particularmay have a molecular weight in the range of about 1000 Daltons (Da) toabout 500,000 Da, preferably in the range of about 5000 to about 200,000Da, and more preferably may have a molecular weight that is sufficientlyhigh to essentially preclude any net absorption through a layer of gutepithelial cells of the compound. In these or other particularembodiments, the phosphate transport inhibitor is modified tosubstantially hinder its net absorption through a layer of gutepithelial cells.

(ii) Persistent Inhibitory Effect

In other embodiments, the substantially impermeable or substantiallysystemically non-bioavailable compounds utilized in the treatmentmethods of the present disclosure may additionally exhibit a persistentinhibitor effect. This effect manifests itself when the inhibitoryaction of a compound at a certain concentration in equilibrium withepithelial cells (e.g., at or above its inhibitory concentration, IC)does not revert to baseline (i.e., phosphate transport withoutinhibitor) after the compound is depleted by simple washing of theluminal content.

This effect can be interpreted as a result of the tight binding of thecompounds to the phosphate transport protein at the intestinal apicalside of the gut epithelial cell. The binding can be considered asquasi-irreversible to the extent that, after the compound has beencontacted with the gut epithelial cell and subsequently washed off saidgut epithelial cell, the flux of phosphate transport is stillsignificantly lower than in the control without the compound. Thispersistent inhibitory effect has the clear advantage of maintaining drugactivity within the GI tract even though the residence time of theactive in the upper GI tract is short, and when no entero-biliaryrecycling process is effective to replenish the compound concentrationnear its site of action.

Such a persistent inhibitory effect has an obvious advantage in terms ofpatient compliance, but also in limiting drug exposure within the GItract.

The persistence effect can be determined using in vitro methods; in oneinstance, cell lines expressing phosphate transporters are split indifferent vials and treated with a phosphate transport inhibitingcompound and phosphate solution to measure the rate of phosphate uptake.The cells in one set of vials are washed for different periods of timeto remove the inhibitor, and phosphate uptake measurement is repeatedafter the washing. Compounds that maintain their inhibitory effect aftermultiple/lengthy washing steps (compared to the inhibitory effectmeasured in the vials where washing does not occur) are persistentinhibitors. Persistence effect can also be characterized ex vivo byusing the everted sac technique, whereby transport of phosphate ismonitored using an excised segment of GI perfused with a solutioncontaining the inhibitor and shortly after flushing the bathing solutionwith a buffer solution free from inhibitor. A persistence effect canalso be characterized in vivo by observing the time needed for phosphatebalance to return to normal when the inhibitor treatment isdiscontinued. The limit of the method resides in the fact that apicalcells (and therefore apical phosphate transporters) are sloughed offafter a period of 3 to 4 days, the typical turnover time of gutepithelial cells. A persistence effect can be achieved by increasing theresidence time of the active compound at the apical surface of the gutepithelial cells; this can be obtained by designing phosphate transportinhibitors with several phosphate transport inhibiting moieties built-inthe small molecule or oligomer (wherein “several” as used hereintypically means at least about 2, about 4, about 6 or more). Examples ofsuch structures in the context of analogs of the antibiotic vancomycinare given in Griffin, et al., J. Am. Chem. Soc., 2003, 125, 6517-6531.Alternatively the compound comprises groups that contribute to increasethe affinity towards the gut epithelial cell so as to increase the timeof contact with the gut epithelial cell surface. Such groups arereferred to as being “mucoadhesive.” More specifically, the Core or Lmoiety can be substituted by such mucoadhesive groups, such aspolyacrylates, partially deacetylated chitosan or polyalkylene glycol.(See also Patil, S. B. et al., Curr. Drug. Deliv., 2008, Oct. 5(4), pp.312-8.)

(iii) GI Enzyme Resistance

Because the compounds utilized in the treatment methods of the presentdisclosure are preferably substantially systemically non-bioavailable,and/or preferably exhibit a persistent inhibitory effect, it is alsodesirable that, during their prolonged residence time in the gut, thesecompounds resist the hydrolytic conditions prevailing in the upper GItract. In such embodiments, compounds of the present disclosure areresistant to phase 1 and phase 2 metabolism. For example, administeredcompounds are preferably resistant to the activity of P450 enzymes,glucurosyl transferases, sulfotransferases, glutathione S-transferases,and the like, in the intestinal mucosa, as well as gastric (e.g.,gastric lipase, and pepsine), pancreatic (e.g., trypsin, triglyceridepancreatic lipase, phospholipase A2, endonucleases, nucleotidases, andalpha-amylase), and brush-border enzymes (e.g., alkaline phosphatase,glycosidases, and proteases) generally known in the art.

The compounds that are utilized in methods of the present disclosure arealso preferably resistant to metabolism by the bacterial flora of thegut; that is, the compounds are not substrates for enzymes produced bybacterial flora. In addition, the compounds administered in accordancewith the methods of the present disclosure may be substantially inactivetowards the gastrointestinal flora, and do not disrupt bacterial growthor survival. As a result, in various embodiments herein, the minimalinhibitory concentration (or “MIC”) against GI flora is desirablygreater than about 15 μg/ml, about 30 μg/ml, about 60 μg/ml, about 120or even about 240 μg/ml, the MIC in various embodiments being forexample between about 16 and about 32 m/ml, or between about 64 andabout 128 μg/ml, or greater than about 256 μg/ml.

To one skilled in the art of medicinal chemistry, metabolic stabilitycan be achieved in a number of ways. Functionality susceptible toP450-mediated oxidation can be protected by, for example, blocking thepoint of metabolism with a halogen or other functional group.Alternatively, electron withdrawing groups can be added to a conjugatedsystem to generally provide protection to oxidation by reducing theelectrophilicity of the compound. Proteolytic stability can be achievedby avoiding secondary amide bonds, or by incorporating changes instereochemistry or other modifications that prevent the drug fromotherwise being recognized as a substrate by the metabolizing enzyme.

(iv) C_(max) and IC₅₀

It is also to be noted that, in various embodiments of the presentdisclosure, one or more of the compounds detailed herein, whenadministered either alone or in combination with one or more additionalpharmaceutically active compounds or agents to a patient in need thereofhas a C_(max) that is less than the IC₅₀ for NaPi2b, more specifically,less than about 10× (10 times) the IC₅₀, and, more specifically still,less than about 100× (100 times) the IC₅₀.

Additionally, or alternatively, it is also to be noted that, in variousembodiments of the present disclosure, one or more of the compoundsdetailed herein, when administered either alone or in combination withone or more additional pharmaceutically active compounds or agents to apatient in need thereof, may have a C_(max) of less than about 10 ng/ml,about 7.5 ng/ml, about 5 ng/ml, about 2.5 ng/ml, about 1 ng/ml, or about0.5 ng/ml, the C_(max) being for example within the range of about 1ng/ml to about 10 ng/ml, or about 2.5 ng/ml to about 7.5 ng/ml.

Additionally, or alternatively, it is also to be noted that, in variousembodiments of the present disclosure, one or more of the compoundsdetailed herein, when administered either alone or in combination withone or more additional pharmaceutically active compounds or agents to apatient in need thereof, may have a IC₅₀ of less than about 10 μM, about7.5 μM, about 5 μM, about 2.5 μM, about 1 μM, or about 0.5 the IC₅₀being for example within the range of about 0.5 μM to about 10 μM, orabout 0.5 μM to about 7.5 μM, or about 0.5 μM to about 5 μM, or about0.5 μM to about 2.5 μM.

Additionally, or alternatively, it is also to be noted that, in variousembodiments of the present disclosure, one or more of compounds detailedherein, when administered to a patient in need thereof, may have a ratioof IC₅₀:C_(max), wherein IC₅₀ and C_(max) are expressed in terms of thesame units, of at least about 10, about 50, about 100, about 250, about500, about 750, or about 1000.

Additionally, or alternatively, it is also to be noted that, in variousembodiments of the present disclosure, wherein one or more of thecompounds as detailed herein is orally administered to a patent in needthereof, within the therapeutic range or concentration, the maximumcompound concentration detected in the serum, defined as C_(max), islower than the NaPi2b inhibitory concentration IC₅₀ of said compound. Aspreviously noted, as used herein, IC₅₀ is defined as the quantitativemeasure indicating the concentration of the compound required to inhibit50% of the NaPi2b transport activity in a cell based assay.

Pharmaceutical Compositions and Methods of Treatment

For the purposes of administration, the compounds of the presentinvention may be administered to a patient or subject as a raw chemicalor may be formulated as pharmaceutical compositions. Pharmaceuticalcompositions of the present invention generally comprise a compound ofthe invention and a pharmaceutically acceptable carrier, diluent orexcipient. The compound is present in the composition in an amount whichis effective to treat a particular disease or condition of interest, asdescribed herein, and preferably with acceptable toxicity to thepatient. The activity of compounds can be determined by one skilled inthe art, for example, as described in the Example below. Appropriateconcentrations and dosages can be readily determined by one skilled inthe art.

A compound or composition of the invention may be used in a method fortreating essentially any disease or other condition in a patient whichwould benefit from phosphate uptake inhibition in the gastrointestinaltract.

For example, by way of explanation, but not limitation, kidney damagereduces the production and activity of renal 1-alpha hydroxylase,leading to lower 1,25-dihydroxy vitamin D. Decreased vitamin D levelslimit gastrointestinal calcium absorption, leading to a decline in serumcalcium levels. The combination of lower 1,25-dihydroxy vitamin D andlower serum calcium levels synergistically stimulate parathyroid tissueto produce and secrete PTH. A loss of nephrons also impairs Piexcretion, but serum P levels are actively defended by the actions ofPTH and FGF-23, and by higher serum P levels, which considerably enhanceurinary PO₄ excretion. However, tubular actions of PTH and FGF-23 cannotmaintain serum P levels in the face of continual nephron loss. Oncerenal insufficiency progresses to the loss of about 40-50% of renalfunction, the decrease in the amount of functioning renal tissue doesnot allow excretion of the full amount of ingested phosphate required tomaintain homeostasis. As a result, hyperphosphatemia develops. Inaddition, a rise in serum P levels impedes renal 1-alpha hydroxylaseactivity, further suppressing activated vitamin D levels, and furtherstimulating PTH, leading to secondary hyperparathyroidism (sHPTH).

Phosphorus imbalance, however, does not necessarily equate withhyperphosphatemia. In fact, the vast majority of CKD patients not yet ondialysis are normophosphatemic but their phosphorus balance is positivewith the excess phosphorus being disposed in the vasculature in the formof ectopic calcification, e.g. intima localized vascular calcification.Clinically, patients with CKD have elevated levels of FGF-23 that aresignificantly associated with deteriorating renal function and withdecreased calcitriol levels, and it has been hypothesized that thesynthesis of FGF-23 is induced by the presence of excess P in the bodyconsecutive to renal failure.

Furthermore, an unrecognized effect on cardiovascular disease ispost-prandial phosphatemia, i.e. serum P excursion secondary to mealintake. Further still, studies have investigated the acute effect ofphosphorus loading on endothelial function in vitro and in vivo.Exposing bovine arotic endothelial cells to a phosphorus load increasedproduction of reactive oxygen species and decreased nitric oxide, aknown vasodilator agent. In the acute P loading study in healthyvolunteers described above, it was found that the flow mediated dilationcorrelated inversely with postprandial serum P (Shuto et al., 2009b, J.Am. Soc. Nephrol., v. 20, no. 7, p. 1504-1512).

Accordingly, in certain more specific embodiments, a compounds orcomposition of the invention can be used in a method selected from thegroup consisting of (a) a method for treating hyperphosphatemia; (b) amethod for treating a renal disease (e.g., chronic kidney disease or endstage renal disease); (c) a method for delaying time to dialysis; (d) amethod for attenuating intima localized vascular calcification; (e) amethod for reducing the hyperphosphatemic effect of active vitamin D;(f) a method for reducing FGF23 levels; (g) a method for attenuatinghyperparathyroidism; (h) a method for improving endothelial dysfunctioninduced by postprandial serum phosphate; (i) a method for reducingurinary phosphorous; (j) a method for normalizing serum phosphoruslevels; (k) a method for treating proteinura; and (1) a method forreducing serum PTH, calcium, calcitriol and/or phosphate concentrationsor levels.

Administration of the compounds of the invention, or theirpharmaceutically acceptable salts, in pure form or in an appropriatepharmaceutical composition, can be carried out via any of the acceptedmodes of administration of agents for serving similar utilities. Thepharmaceutical compositions of the invention can be prepared bycombining a compound of the invention with an appropriatepharmaceutically acceptable carrier, diluent or excipient, and may beformulated into preparations in solid, semi-solid, liquid or gaseousforms, such as tablets, capsules, powders, granules, ointments,solutions, suppositories, injections, inhalants, gels, microspheres, andaerosols. Typical routes of administering such pharmaceuticalcompositions include, without limitation, oral, topical, transdermal,inhalation, parenteral, sublingual, buccal, rectal, vaginal, andintranasal. The term parenteral as used herein includes subcutaneousinjections, intravenous, intramuscular, intrasternal injection orinfusion techniques. Pharmaceutical compositions of the invention areformulated so as to allow the active ingredients contained therein to bebioavailable upon administration of the composition to a patient.Compositions that will be administered to a subject or patient take theform of one or more dosage units, where for example, a tablet may be asingle dosage unit, and a container of a compound of the invention inaerosol form may hold a plurality of dosage units. Actual methods ofpreparing such dosage forms are known, or will be apparent, to thoseskilled in this art; for example, see Remington: The Science andPractice of Pharmacy, 20th Edition (Philadelphia College of Pharmacy andScience, 2000). The composition to be administered will, in any event,contain a therapeutically effective amount of a compound of theinvention, or a pharmaceutically acceptable salt thereof, for treatmentof a disease or condition of interest in accordance with the teachingsof this invention.

A pharmaceutical composition of the invention may be in the form of asolid or liquid. In one aspect, the carrier(s) are particulate, so thatthe compositions are, for example, in tablet or powder form. Thecarrier(s) may be liquid, with the compositions being, for example, anoral syrup, injectable liquid or an aerosol, which is useful in, forexample, inhalatory administration.

When intended for oral administration, the pharmaceutical composition ispreferably in either solid or liquid form, where semi-solid,semi-liquid, suspension and gel forms are included within the formsconsidered herein as either solid or liquid.

As a solid composition for oral administration, the pharmaceuticalcomposition may be formulated into a powder, granule, compressed tablet,pill, capsule, chewing gum, wafer or the like form. Such a solidcomposition will typically contain one or more inert diluents or ediblecarriers. In addition, one or more of the following may be present:binders such as carboxymethylcellulose, ethyl cellulose,microcrystalline cellulose, gum tragacanth or gelatin; excipients suchas starch, lactose or dextrins, disintegrating agents such as alginicacid, sodium alginate, Primogel, corn starch and the like; lubricantssuch as magnesium stearate or Sterotex; glidants such as colloidalsilicon dioxide; sweetening agents such as sucrose or saccharin; aflavoring agent such as peppermint, methyl salicylate or orangeflavoring; and a coloring agent.

When the pharmaceutical composition is in the form of a capsule, forexample, a gelatin capsule, it may contain, in addition to materials ofthe above type, a liquid carrier such as polyethylene glycol or oil.

The pharmaceutical composition may be in the form of a liquid, forexample, an elixir, syrup, solution, emulsion or suspension. The liquidmay be for oral administration or for delivery by injection, as twoexamples. When intended for oral administration, preferred compositioncontain, in addition to the present compounds, one or more of asweetening agent, preservatives, dye/colorant and flavor enhancer. In acomposition intended to be administered by injection, one or more of asurfactant, preservative, wetting agent, dispersing agent, suspendingagent, buffer, stabilizer and isotonic agent may be included.

The liquid pharmaceutical compositions of the invention, whether they besolutions, suspensions or other like form, may include one or more ofthe following adjuvants: sterile diluents such as water for injection,saline solution, preferably physiological saline, Ringer's solution,isotonic sodium chloride, fixed oils such as synthetic mono ordiglycerides which may serve as the solvent or suspending medium,polyethylene glycols, glycerin, propylene glycol or other solvents;antibacterial agents such as benzyl alcohol or methyl paraben;antioxidants such as ascorbic acid or sodium bisulfite; chelating agentssuch as ethylenediaminetetraacetic acid; buffers such as acetates,citrates or phosphates and agents for the adjustment of tonicity such assodium chloride or dextrose. The parenteral preparation can be enclosedin ampoules, disposable syringes or multiple dose vials made of glass orplastic. Physiological saline is a preferred adjuvant. An injectablepharmaceutical composition is preferably sterile.

A liquid pharmaceutical composition of the invention intended for eitherparenteral or oral administration should contain an amount of a compoundof the invention such that a suitable dosage will be obtained.

The pharmaceutical composition of the invention may be intended fortopical administration, in which case the carrier may suitably comprisea solution, emulsion, ointment or gel base. The base, for example, maycomprise one or more of the following: petrolatum, lanolin, polyethyleneglycols, bee wax, mineral oil, diluents such as water and alcohol, andemulsifiers and stabilizers. Thickening agents may be present in apharmaceutical composition for topical administration. If intended fortransdermal administration, the composition may include a transdermalpatch or iontophoresis device.

The pharmaceutical composition of the invention may be intended forrectal administration, in the form, for example, of a suppository, whichwill melt in the rectum and release the drug. The composition for rectaladministration may contain an oleaginous base as a suitablenonirritating excipient. Such bases include, without limitation,lanolin, cocoa butter and polyethylene glycol.

The pharmaceutical composition of the invention may include variousmaterials, which modify the physical form of a solid or liquid dosageunit. For example, the composition may include materials that form acoating shell around the active ingredients. The materials that form thecoating shell are typically inert, and may be selected from, forexample, sugar, shellac, and other enteric coating agents.Alternatively, the active ingredients may be encased in a gelatincapsule.

The pharmaceutical composition of the invention in solid or liquid formmay include an agent that binds to the compound of the invention andthereby assists in the delivery of the compound. Suitable agents thatmay act in this capacity include a monoclonal or polyclonal antibody, aprotein or a liposome.

The pharmaceutical composition of the invention may consist of dosageunits that can be administered as an aerosol. The term aerosol is usedto denote a variety of systems ranging from those of colloidal nature tosystems consisting of pressurized packages. Delivery may be by aliquefied or compressed gas or by a suitable pump system that dispensesthe active ingredients. Aerosols of compounds of the invention may bedelivered in single phase, bi-phasic, or tri-phasic systems in order todeliver the active ingredient(s). Delivery of the aerosol includes thenecessary container, activators, valves, subcontainers, and the like,which together may form a kit. One skilled in the art, without undueexperimentation may determine preferred aerosols.

The pharmaceutical compositions of the invention may be prepared bymethodology well known in the pharmaceutical art. For example, apharmaceutical composition intended to be administered by injection canbe prepared by combining a compound of the invention with sterile,distilled water so as to form a solution. A surfactant may be added tofacilitate the formation of a homogeneous solution or suspension.Surfactants are compounds that non-covalently interact with the compoundof the invention so as to facilitate dissolution or homogeneoussuspension of the compound in the aqueous delivery system.

The compounds of the invention, or their pharmaceutically acceptablesalts, are administered in a therapeutically effective amount, whichwill vary depending upon a variety of factors including the activity ofthe specific compound employed; the metabolic stability and length ofaction of the compound; the age, body weight, general health, sex, anddiet of the patient; the mode and time of administration; the rate ofexcretion; the drug combination; the severity of the particular disorderor condition; and the subject undergoing therapy.

In certain embodiments, a typical dosage of the substantiallyimpermeable or substantially systemically non-bioavailable, compound maybe between about 0.2 mg per day and about 2 g per day, or between about1 mg and about 1 g per day, or between about 5 mg and about 500 mg, orbetween about 10 mg and about 250 mg per day, which is administered to asubject in need of treatment.

The frequency of administration of the compounds and compositionsdescribed herein may vary from once-a-day (QD) to twice-a-day (BID) orthrice-a-day (TID), etc., the precise frequency of administrationvarying with, for example, the patient's condition, the dosage, etc.

Compounds of the invention, or pharmaceutically acceptable derivativesthereof, may also be administered simultaneously with, prior to, orafter administration of one or more other therapeutic agents. Suchcombination therapy includes administration of a single pharmaceuticaldosage formulation which contains a compound of the invention and one ormore additional active agents, as well as administration of the compoundof the invention and each active agent in its own separatepharmaceutical dosage formulation. For example, a compound of theinvention and the other active agent can be administered to the patienttogether in a single oral dosage composition such as a tablet orcapsule, or each agent administered in separate oral dosageformulations. Where separate dosage formulations are used, the compoundsof the invention and one or more additional active agents can beadministered at essentially the same time, i.e., concurrently, or atseparately staggered times, i.e., sequentially; combination therapy isunderstood to include all these regimens.

For example, in certain embodiments, the additional biologically activeagent included in a pharmaceutical composition (or method) of theinvention is selected, for example, from vitamin D₂ (ergocalciferol),vitamin D₃ (cholecalciferol), active vitamin D (calcitriol) and activevitamin D analogs (e.g. doxercalciferol, paricalcitol).

In other specific embodiments, the additional biologically active agentincluded in a pharmaceutical composition (or method) of the invention isa phosphate binder, such as Renvela, Renagel, Fosrenol, calciumcarbonate, calcium acetate (e.g. Phoslo), MCI-196, Zerenex™, Fermagate,APS1585, SBR-759, PA-21, and the like.

The compounds of the invention have been found to act synergisticallywith phosphate binders by providing a higher efficacy than the sum ofthe efficacy of a NaPi2b inhibitor and that of a phosphate binderadministered alone. Without wishing to be bound by theory, it isbelieved that the synergy results from the distinct mechanisms of actionof a phosphate transport inhibitor and a phosphate binder. Morespecifically, a phosphate transport inhibitor blocks the epithelialinward transport of phosphate ions whereas phosphate binders sequesterfree phosphate ions in the lumen of the intestine.

The efficacy of a phosphate binder, as measured by its vivo bindingcapacity (mole of phosphate ions bound per gram of binder) isessentially dictated by: i) the density of binding sites (i.e. aminegroups in Renvela/Sevelamer, a polymeric amine material; or multivalentcations such calcium or lanthanum in Phoslo (Calcium acetate) orFosrenol (lanthanum carbonate)); and ii) the affinity of said bindingsites for phosphate ions. Notably only a fraction of the binding sitesis available for phosphate binding in vivo as other anions, such as bileacids and fatty acids compete for the binding sites and therefore lowersefficacy. Bound phosphate ions are in equilibrium with free phosphate inthe intestinal lumen and are themselves subject to intense pumping fromphosphate transport proteins lining up the epithelia. Experiments haveshown that the efficacy of phosphate intestinal uptake is remarkablyhigh, exceeding 95% of the phosphate presented to the epithelia. It isbelieved that the active transport of phosphate contributes to lower theluminal free phosphate concentration and therefore to drive the bindingequilibrium of a phosphate binder to lower binding capacity. It is alsobelieved that by reducing the phosphate intestinal transport using aphosphate transport inhibitor, one restores a higher in vivo bindingcapacity of phosphate sequestering agents. The synergistic effect isthought to be even more pronounced when the contribution of activephosphate transport is increased as a result of, e.g. vitamin Dtreatment, an agent promoting NaPi2b expression.

It is understood that in the present description, combinations ofsubstituents and/or variables of the depicted formulae are permissibleonly if such contributions result in stable compounds.

It will also be appreciated by those skilled in the art that in theprocess described herein the functional groups of intermediate compoundsmay need to be protected by suitable protecting groups. Such functionalgroups include hydroxy, amino, mercapto and carboxylic acid. Suitableprotecting groups for hydroxy include trialkylsilyl or diarylalkylsilyl(for example, t-butyldimethylsilyl, t-butyldiphenylsilyl ortrimethylsilyl), tetrahydropyranyl, benzyl, and the like. Suitableprotecting groups for amino, amidino and guanidino includet-butoxycarbonyl, benzyloxycarbonyl, and the like. Suitable protectinggroups for mercapto include —C(O)—R″ (where R″ is alkyl, aryl orarylalkyl), p-methoxybenzyl, trityl and the like. Suitable protectinggroups for carboxylic acid include alkyl, aryl or arylalkyl esters.Protecting groups may be added or removed in accordance with standardtechniques, which are known to one skilled in the art and as describedherein. The use of protecting groups is described in detail in Green, T.W. and P. G. M. Wutz, Protective Groups in Organic Synthesis (1999), 3rdEd., Wiley. As one of skill in the art would appreciate, the protectinggroup may also be a polymer resin such as a Wang resin, Rink resin or a2-chlorotrityl-chloride resin.

It will also be appreciated by those skilled in the art, although suchprotected derivatives of compounds of this invention may not possesspharmacological activity as such, they may be administered to a mammaland thereafter metabolized in the body to form compounds of theinvention which are pharmacologically active. Such derivatives maytherefore be described as “prodrugs”. All prodrugs of compounds of thisinvention are included within the scope of the invention.

Furthermore, all compounds of the invention which exist in free base oracid form can be converted to their pharmaceutically acceptable salts bytreatment with the appropriate inorganic or organic base or acid bymethods known to one skilled in the art. Salts of the compounds of theinvention can be converted to their free base or acid form by standardtechniques.

The following Examples illustrate various representative methods ofmaking compounds of this invention, i.e., compounds of structure (I), ora stereoisomer, prodrug or pharmaceutically acceptable salt thereof. Itis understood that one skilled in the art may be able to make thesecompounds by similar methods or by combining other methods known to oneskilled in the art. It is also understood that one skilled in the artwould be able to make, in a similar manner as described below, othercompounds of structure (I) not specifically illustrated below by usingthe appropriate starting components and modifying the parameters of thesynthesis as needed. In general, starting components may be obtainedfrom sources such as Sigma Aldrich, Lancaster Synthesis, Inc.,Maybridge, Matrix Scientific, TCI, and Fluorochem USA, etc. orsynthesized according to sources known to those skilled in the art (see,e.g., Advanced Organic Chemistry: Reactions, Mechanisms, and Structure,5th edition (Wiley, December 2000)) or prepared as described in thisinvention.

The following examples are provided for purposes of illustration, notlimitation.

EXAMPLES Example 13-(3-((4-(Piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenyl)carbamoyl)benzylthio)propanoicacid

Scheme 1.

1. HOCH₂CH₂OH, TsOH, toluene; 2. piperidine; 3. HCl; 4. PhSO₂Cl, NaH; 5.LDA, intermediate 1c; 6. DMSO, oxalyl dichloride; 7. H₂, Pd/C; 8. methylacrylate, DBU, acetonitrile; 9. oxaloyl chloride, dichloromethane; 10.intermediates 1g and 1i, pyridine; 11. Tetrabutylammonium fluoride; 11.LiOH.

Intermediate 1a: 2-(5-Chloro-2-nitrophenyl)-1,3-dioxolane

Into a 250 mL 3-neck round bottom flask was placed a solution of5-chloro-2-nitrobenzaldehyde (7.6 g, 40.86 mmol, 1.00 equiv) in toluene(150 mL), ethane-1,2-diol (2.9 g, 46.77 mmol), and p-toluenesulfonicacid monohydrate (350 mg, 2.03 mmol, 0.05 equiv). The resulting solutionwas heated to reflux under a Dean-Stark trap overnight. The resultingmixture was diluted with 300 mL of water. The solution was extractedwith 3×100 mL of ethyl acetate and the organic layers combined. Theresulting mixture was washed with 1×300 mL of brine. The mixture wasdried over anhydrous sodium sulfate and concentrated under vacuum. Thisresulted in 9.3 g (99%) of intermediate 1a as a brown oil that was usedwithout further characterization.

Intermediate 1b. 1-(3-(1,3-Dioxolan-2-yl)-4-nitrophenyl)piperidine

Into a 500 mL round bottom flask, was placed2-(5-chloro-2-nitrophenyl)-1,3-dioxolane (9.3 g, 40.43 mmol, 1.00 equiv)and piperidine (172 g, 2.02 mol, 50.04 equiv). The resulting solutionwas heated to reflux overnight. The mixture was concentrated undervacuum. The resulting solution was diluted with 100 mL ofdichloromethane and 200 mL of water. The phases were separated and theresulting solution was extracted with 3×100 mL of dichloromethane. Theorganic layers were combined. The mixture was washed with 1×200 mL ofbrine. The mixture was dried over anhydrous sodium sulfate andconcentrated under vacuum. This resulted in 11 g (98%) of intermediate1b as brown oil.

Intermediate 1c: 2-Nitro-5-(piperidin-1-yl)benzaldehyde

Into a 500 mL round bottom flask, was placed a solution of1-(3-(1,3-dioxolan-2-yl)-4-nitrophenyl)piperidine (11 g, 39.57 mmol,1.00 equiv) in tetrahydrofuran (250 mL), water (100 mL), and 3Nhydrochloric acid (50 mL). The resulting solution was heated to refluxfor 2 h in an oil bath. The mixture was concentrated under vacuum. Thesolids were collected by filtration. The filter cake was washed with2×40 mL of water and 2×40 mL of hexane. This resulted in 9 g (97%) ofintermediate 1c as a yellow solid.

Intermediate 1d: 1-(Phenylsulfonyl)-6-(trifluoromethyl)-1H-indole

Into a 100 mL 3-neck round bottom flask purged and maintained with aninert atmosphere of nitrogen, was placed a solution of6-(trifluoromethyl)-1H-indole (3.7 g, 20.00 mmol, 1.00 equiv) inN,N-dimethylformamide (50 mL). This was followed by the addition ofsodium hydride (750 mg, 21.88 mmol, 1.09 equiv, 70%) in several batchesat 0° C. The resulting solution was stirred for 1 h at 0° C. in anice/salt bath. To this was added benzenesulfonyl chloride (3.90 g, 22.03mmol, 1.10 equiv) dropwise with stirring at 0° C. The resulting solutionwas stirred for 1 h at 0° C. The solution was diluted with 100 mL ofwater. The solids were collected by filtration. The residue was appliedonto a silica gel column and eluted with ethyl acetate/PE (1:10). Thisresulted in 4 g (60%) of intermediate 1d as a yellow solid.

Intermediate 1e:(2-Nitro-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indol-2-yl)methanol

Into a 50 mL 3-neck round bottom flask purged and maintained with aninert atmosphere of nitrogen was placed a solution of diisopropylamine(888 mg, 8.79 mmol, 1.90 equiv) in tetrahydrofuran (5 mL). This wasfollowed by the addition of n-BuLi (3.7 mL, 2.5M) dropwise with stirringat −20° C. The mixture was warmed to 0° C. slowly and stirred for 30min. To this was added a solution of1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole (1.5 g, 4.62 mmol, 1.00equiv) in tetrahydrofuran (5 mL) dropwise with stirring at −80° C. Themixture was warmed to 0° C. slowly and stirred for 1 h. To the mixturewas added a solution of 2-nitro-5-(piperidin-1-yl)benzaldehyde (1.08 g,4.62 mmol, 1.00 equiv) in tetrahydrofuran (5 mL) dropwise with stirringat −80° C. The mixture was stirred for 30 min at 80° C. and then 4 h atroom temperature. The reaction was then quenched by the addition of 5 mLof water. The resulting solution was extracted with 20 mL of ethylacetate and the organic layers combined and dried over sodium sulfateand concentrated under vacuum. The residue was applied onto a silica gelcolumn and eluted with ethyl acetate/PE (1:10). This resulted in 1.2 g(46%) of intermediate 1e as a yellow solid.

Intermediate 1f:(2-Nitro-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-(trifluoro-methyl)-1H-indol-2-yl)methanone

Into a 50 mL 3-neck round bottom flask purged and maintained with aninert atmosphere of nitrogen, was placed a solution of dimethlysulfoxide(156 mg, 2.00 mmol, 3.73 equiv) in dichloromethane (5 mL). This wasfollowed by the addition of oxalyl dichloride (127 mg, 1.00 mmol, 1.87equiv) dropwise with stirring at −80° C. The resulting solution wasstirred for 10 min at −80° C. in a liquid nitrogen bath. To this wasadded a solution of(2-nitro-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indol-2-yl)methanol(300 mg, 0.54 mmol, 1.00 equiv) in dichloromethane (5 mL) dropwise withstirring at −80° C. The resulting solution was stirred for an additional60 min at −80° C. To the mixture was added triethylamine (400 mg, 3.96mmol, 7.39 equiv) dropwise with stirring at −80° C. The resultingsolution allowed to warm to −20° C. over 60 minutes. The solution wasdiluted with 50 mL of DCM. The mixture was washed with 1×30 mL of waterand 1×30 mL of brine. The mixture was dried over anhydrous sodiumsulfate and concentrated under vacuum. This resulted in 300 mg ofintermediate if as orange oil.

Intermediate 1g:(2-Amino-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-trifluoro-methyl)-1H-indol-2-yl)methanone

Into a 50 mL 3-neck round bottom flask purged and maintained with aninert atmosphere of nitrogen, was placed a solution of(2-nitro-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indol-2-yl)methanone(300 mg, 0.51 mmol, 1.00 equiv, 95%) in methanol (10 mL), and wetpalladium on carbon (0.15 g). The resulting solution was stirredovernight at 10° C. under an atmosphere of hydrogen gas. The mixture wasfiltered. The filtrate was concentrated under vacuum. This resulted in0.25 g (88%) of intermediate 1g as a red solid.

Intermediate 1h: (3-((3-Methoxy-3-oxopropylthio)methyl)benzoic acid

Into a 50-mL round-bottom flask purged and maintained with an inertatmosphere of nitrogen, was added a solution of3-(mercaptomethyl)benzoic acid (500 mg, 2.97 mmol, 1.00 equiv) inacetonitrile (10.0 mL), followed by methyl acrylate (10.0 mL) and1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU; 1.0 g, 6.57 mmol, 2.00 equiv).The resulting solution was heated to reflux overnight, then concentratedunder vacuum and the residue was applied onto a silica gel column,eluting with ethyl acetate/petroleum ether (0-1:6). This resulted in 220mg (28%) of intermediate 1h as light-red oil.

Intermediate 1i: Methyl 3-(3-(chlorocarbonyl)benzylthio)propanoate

Into a 50-mL round-bottom flask purged and maintained with an inertatmosphere of nitrogen, was placed a solution of3-((3-methoxy-3-oxopropylthio)methyl)benzoic acid (61.6 mg, 0.24 mmol,1.00 equiv) in dichloromethane (5 mL). This was followed by the additionof oxaloyl dichloride (121.76 mg, 0.96 mmol, 4.00 equiv) dropwise withstirring at room temperature. Then a few drops of N,N-dimethylformamidewas addded as catalyst and the resulting solution was heated to refluxfor 30 min. The reaction mixture was concentrated under vacuum to afford60 mg (crude) of intermediate 1i as yellow oil.

Intermediate 1j: Methyl3-(3-((2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenyl)carbamoyl)benzylthio)propanoate

Into a 50 mL 3-neck round bottom flask was placed a solution of(2-amino-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indol-2-yl)methanone(300 mg, 0.57 mmol, 1.00 equiv) in tetrahydrofuran (10 mL) and asolution of methyl 3-(3-(chlorocarbonyl)benzylthio)propanoate (180 mg,0.66 mmol, 1.16 equiv) in tetrahydrofuran (3 mL). This was followed bythe addition of pyridine (80 mg, 1.01 mmol, 1.78 equiv) dropwise withstirring. The solution was stirred for 3 h at 10° C.

The resulting solution was diluted with 50 mL of ethyl acetate. Themixture was washed with 1×30 mL of water and 1×30 mL of brine. Themixture was dried over anhydrous sodium sulfate and concentrated undervacuum. This resulted in 0.4 g intermediate 1j as red oil.

Intermediate 1k: Methyl3-(3-((4-(piperidin-1-1)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenyl)carbamoyl)benzylthio)propanoate

Into a 50 mL 3-neck round bottom flask, was placed a solution of methyl3-(3-((2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenyl)carbamoyl)benzylthio)propanoate(300 mg, 0.33 mmol, 1.00 equiv, 85%) in methanol (5 mL), and 5 mL of a1M solution of tetrabutylammonium fluoride in THF. The resultingsolution was heated to reflux for 6 h in an oil bath. The solution wasdiluted with 30 mL of ethyl acetate. The resulting mixture was washedwith 1×20 mL of water and 1×20 mL of brine. The mixture was dried overanhydrous sodium sulfate and concentrated under vacuum. The residue wasapplied onto a silica gel column and eluted with ethyl acetate/petroleumether (1:5). This resulted in 150 mg (72%) of intermediate 1k as a redsolid.

Example 13-(3-((4-Piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)-phenyl)-carbamoyl)benzylthio)propanoicacid

Into a 50 mL round bottom flask, was placed a solution of methyl3-(3-((4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenyl)carbamoyl)benzylthio)-propanoate(60 mg, 0.10 mmol, 1.00 equiv) in tetrahydrofuran (5 mL), and a solutionof lithium hydroxide hydrate (100 mg, 2.50 mmol, 26.00 equiv) in water(2 mL). The solution was stirred overnight at 15° C. The solution wasthen diluted with 30 mL of water. The mixture was washed with 1×20 mL ofethyl acetate. The pH value of the solution was adjusted to 5 with 1Nhydrochloric acid. The resulting solution was extracted with 2×30 mL ofethyl acetate and the organic layers combined and dried over anhydroussodium sulfate and concentrated under vacuum. The residue was dissolvedin 2 mL of ether. The product was precipitated by the addition ofhexane. The solids were collected by filtration. This resulted in 20 mg(34%) of3-(3-((4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenyl)-carbamoyl)-benzylthio)-propanoicacid as a orange solid. ¹H-NMR (300 MHz, DMSO, ppm): δ 12.30 (1H, s),10.36 (s, 1H), 7.94-7.91 (d, 1H), 7.76 (s, 1H), 7.68-7.58 (m, 2H), 7.65(s, 1H), 7.47-7.44 (d, 1H), 7.40-7.32 (m, 2H), 7.25-7.24 (d, 2H), 7.12(s, 1H), 3.74 (s, 2H), 3.19 (s, 4H), 2.5 (m, 4H), 1.56-1.64 (m, 6H), MS(ES, m/z): 610 [M+H]⁺.

Example 2N1-Methyl-N1-(2-morpholinoethyl)-N3-(4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenyl)isophthalamide2,2,2-trifluoroacetate

Scheme 2.

1. oxalyl dichloride, DCM, DMF; 2. (Boc)₂O, TEA, DCM; 3. LiAlH₄, THF; 4.Intermediate 2a, DCM, TEA; 5. LiOH, THF, H₂O; 6. oxalyl dichloride, DMF;7. Intermediate 1g, pyridine; 8. Tetrabutylammonium fluoride.

Intermediate 2a: Methyl 3-(chlorocarbonyl)benzoate

To a solution of 3-(methoxycarbonyl)benzoic acid (6.2 g, 34.44 mmol,1.00 equiv) in dichloromethane (50 mL) was added oxalyl dichloride (8.74g, 69.37 mmol, 2.00 equiv) and N,N-dimethylformamide (DMF; cat.) and theresulting solution was stirred for 1 h at 40° C. in an oil bath. Theresulting mixture was concentrated under vacuum to afford 6.6 g (87%) ofintermediate 2a as brown oil.

Intermediate 2b: Tert-butyl2-morpholinoethylcarbamate

To 2-morpholinoethanamine (10 g, 76.92 mmol, 1.00 equiv) indichloromethane (50 mL) was added triethylamine (5.83 g, 57.72 mmol,0.50 equiv). This was followed by the addition of Di-tert-butyldicarbonate (18.44 g, 84.59 mmol, 1.10 equiv) at 0-5° C. and theresulting solution was stirred overnight at 25° C. The reaction mixturewas diluted with 200 mL of dichloromethane and then washed with 1×30 mLof 10% sodium bicarbonate and 1×30 mL of brine. The organic layer wasdried over sodium sulfate and concentrated under vacuum to afford 16 g(81%) of intermediate 2b as an off-white solid.

Intermediate 2c: N-Methyl-2-morpholinoethanamine

To a solution of LiAlH4 (7.72 g, 208.65 mmol, 3.00 equiv) intetrahydrofuran (THF; 60 mL) stirring at 0-5° C. was added dropwise asolution of tert-butyl 2-morpholinoethylcarbamate (16 g, 62.61 mmol,1.00 equiv, 90%) in THF (40 mL). The resulting solution was stirred for2 h at 70° C. in a oil bath, allowed to cool and then quenched by theaddition of 7.7 mL of water, 7.7 mL of 15% sodium hydroxide and 23.1 mLof water. The solids were filtered out, then the mixture was dried oversodium sulfate and concentrated under vacuum. The residue was appliedonto a silica gel column, eluting with dichloromethane:methanol (0.5%triethylamine) (20:1) to afford 4.2 g (42%) of intermediate 2c as brownoil.

Intermediate 2d: Methyl 3-(methyl(2-morpholinoethyl)carbamoyl)benzoate

To a solution of N-methyl-2-morpholinoethanamine (2.1 g, 13.12 mmol,1.00 equiv, 90%) in dichloromethane (20 mL) at 0-5° C. was addedtriethylamine (1.47 g, 14.55 mmol, 1.00 equiv) followed by the dropwiseaddition of a solution of methyl 3-(chlorocarbonyl)benzoate (3.3 g,15.00 mmol, 1.20 equiv, 90%) in dichloromethane (10 mL). The resultingsolution was stirred for 3 h at room temperature. The mixture was thendiluted with 100 mL of dichloromethane and then washed with 1×30 mL of10% sodium bicarbonate and 1×30 mL of brine. The organic layer was driedover sodium sulfate, concentrated under vacuum, and the residue wasapplied onto a silica gel column eluting with dichloromethane:methanol(20:1) to afford 4.4 g (99%) of intermediate 2d as a brown solid.

Intermediate 2e: 3-(Methyl(2-morpholinoethyl)carbamoyl)benzoic acid

To a solution of methyl 3-(methyl(2-morpholinoethyl)carbamoyl)benzoate(4.4 g, 13.66 mmol, 1.00 equiv, 95%) in tetrahydrofuran/water (15/10 mL)was added lithium hydroxide hydrate (1.77 g, 43.17 mmol, 3.00 equiv) andthe resulting solution was stirred for 1 h at 25° C. The resultingmixture was concentrated under vacuum, diluted with 10 mL of water, andthe pH value of the solution was adjusted to 2-3 with hydrogen chloride.The resulting mixture was washed with 2×30 mL of ethyl acetate, and thenthe aqueous layer was concentrated under vacuum. The residue was appliedonto a silica gel column with ethyl acetate:methanol (4:1) to afford 2.7g (65%) of intermediate 2e as a white solid.

Intermediate 2f: 3-(Methyl(2-morpholinoethyl)carbamoyl)benzoyl chloride

Into a 50 mL round bottom flask was placed3-(methyl(2-morpholinoethyl)carbamoyebenzoic acid (300 mg, 1.03 mmol,1.00 equiv), oxalyl dichloride (6 mL), and N,N-dimethylformamide (1drop). The resulting solution was stirred for 2 h at room temperature.The resulting mixture was concentrated under vacuum. This resulted in300 mg (94%) intermediate 2f as a white solid.

Intermediate 2g:N1-Methyl-N1-(2-morpholinoethyl)-N3-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenyl)isophthalamide

Into a 50 mL round bottom flask was placed a solution of(2-amino-5-(piperidin-1-yl)phenyl)(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indol-2-yl)methanone(20 mg, 0.04 mmol, 1.00 equiv) in dichloromethane (5 mL), pyridine (30mg, 0.38 mmol, 10.00 equiv), and3-(methyl(2-morpholinoethyl)carbamoyl)benzoyl chloride (18 mg, 0.06mmol, 1.50 equiv). The resulting solution was stirred for 2 h at roomtemperature. The mixture was washed with 1×50 mL of water. The mixturewas concentrated under vacuum. The crude product was washed with water.This resulted in 20 mg (66%) of intermediate 2g as red oil.

Example 2N1-Methyl-N1-(2-morpholinoethyl)-N3-(4-(piperidin-1-yl)-2-(6-(trifluoro-methyl)-1H-indole-2-carbonyl)phenyl)isophthalamide2,2,2-trifluoroacetate

Into a 50 mL round bottom flask was placed a solution ofN1-methyl-N1-(2-morpholinoethyl)-N3-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenyl)-isophthalamide(300 mg, 0.37 mmol, 1.00 equiv) in methanol (7 mL), and 7 mL of a 1Nsolution of tetrabutylammonimu fluoride in THF. The resulting solutionwas stirred overnight at 85° C. The mixture was concentrated undervacuum. The residue was dissolved in 50 mL of ethyl acetate. Theresulting mixture was washed with 4×50 mL of water. The mixture wasdried over sodium sulfate and concentrated under vacuum. The crudeproduct (300 mg) was purified by reverse phase (C18) HPLC, eluting withwater (0.05% TFA) and CH₃CN (0.05% TFA) gradient (25%-44% CH₃CN over 6min) to afford 202 mg (68%) ofN1-methyl-N1-(2-morpholinoethyl)-N3-(4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenyl)isophthalamide2,2,2-trifluoroacetate as a yellow solid. ¹H-NMR (300 MHz, CD₃OD, ppm):δ 8.28 (d, J=9.0 Hz, 1H), 8.02 (m, 2H), 7.94 (m, 2H), 7.84 (s, 1H), 7.71(m, 2H), 7.62 (m, 1H), 7.35 (m, 1H), 7.26 (s, 1H), 4.11 (m, 2H), 3.93(m, 3H), 3.77 (m, 3H), 3.53 (m, 6H), 3.32 (m, 2H), 3.06 (s, 3H), 1.94(m, 4H), 1.77 (m, 2H). MS (ES, m/z): 662 [M+H]⁺.

Example 3N-(2-Methoxyethyl)-3-(3-(4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenylcarbamoyl)benzylthio)benzamide

Scheme 3.

1. Intermediate 1g, pyridine, dichloromethane; 2,3-mercaptobenzoic acid,Et₃N; 3. methoxyethylamine, EDC.HCl, DMAP; 4. TBAF.

Intermediate 3 a:3-(Bromomethyl)-N-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenyl)benzamide

Intermediate 3a was prepared from 3-(bromomethyl)benzoylchloride andintermediate 1g by a procedure similar to that used to prepareintermediate 1h.

Intermediate 3b:3-(3-(2-(1-(Phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenylcarbamoyl)benzylthio)benzoicacid

Into a 100-mL round-bottom flask was placed a solution of3-(bromomethyl)-N-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenyl)benzamide(200 mg, 0.28 mmol, 1.00 equiv) in acetonitrile (20 mL),3-mercaptobenzoic acid (50 mg, 0.32 mmol, 1.20 equiv), and triethylamine(90 mg, 0.89 mmol, 3.00 equiv). The resulting solution was stirredovernight at 45° C. The resulting mixture was concentrated under vacuum.The residue was dissolved in 60 ml of ethyl acetate. The resultingmixture was washed with 2×30 mL of water. The mixture was dried oversodium sulfate and concentrated under vacuum. This resulted in 200 mg ofintermediate 3b as a red solid.

Intermediate 3c:N-(2-Methoxyethyl)-3-(3-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenylcarbamoyl)-benzylthio)benzamide

Into a 100-mL round-bottom flask, was placed a solution of3-(3-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenylcarbamoyl)benzylthio)-benzoicacid (220 mg, 0.28 mmol, 1.00 equiv) in dichloromethane (20 mL), EDCHCl(80 mg, 0.42 mmol, 1.50 equiv), 4-dimethylaminopyridine (51 mg, 0.41mmol, 1.50 equiv), and 2-methoxyethanamine (42 mg, 0.56 mmol, 2.00equiv). The resulting solution was stirred for 2 h at 25° C. Theresulting mixture was washed with 2×10 mL of aqueous NH₄Cl. The mixturewas dried over anhydrous sodium sulfate and concentrated under vacuum.This resulted in 200 mg (85%) of intermediate 3c as a red solid.

Example 3N-(2-Methoxyethyl)-3-(3-(4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)phenylcarbamoyl)benzylthio)benzamide

Into a 50-mL round-bottom flask was placed a solution ofN-(2-methoxyethyl)-3-(3-(2-(1-(phenylsulfonyl)-6-(trifluoromethyl)-1H-indole-2-carbonyl)-4-(piperidin-1-yl)phenylcarbamoyl)benzylthio)-benzamide(200 mg, 0.23 mmol, 1.00 equiv) in methanol (3.5 mL), and 3.5 mL of a1.0 N solution of tetrabutylammonium fluoride in THF. The resultingsolution was stirred overnight at 80° C. The resulting mixture wasconcentrated under vacuum. The residue was dissolved in 50 mL of ethylacetate. The resulting mixture was washed with 3×20 mL of water. Themixture was dried over anhydrous sodium sulfate and concentrated undervacuum. The crude product (100 mg) was purified by HPLC with thefollowing conditions (Waters 2767-3): Column, SunFire Prep C18, 19×150mm Sum; mobile phase, water with 0.05% TFA and CH₃CN (gradient of 49% to61% CH₃CN over 6 min); Detector, Waters 2545 UV Detector 254 and 270 nm.This resulted in 38.1 mg (17%) ofN-(2-methoxyethyl)-3-(3-(4-(piperidin-1-yl)-2-(6-(trifluoromethyl)-1H-indole-2-carbonyl)-phenylcarbamoyl)benzylthio)benzamideas a orange solid. ¹H-NMR (300 MHz, CD₃OD, ppm): δ 8.38 (d, J=9 Hz, 1H),8.01 (d, J=3 Hz, 1H), 7.91-7.87 (m, 2H), 7.78-7.73 (m, 4H), 7.62-7.59(m, 1H), 7.53-7.51 (m, 1H), 7.47-7.26 (m, 5H), 4.23 (s, 2H), 3.62-3.57(m, 4H), 3.53 (s, 3H), 3.35-3.34 (m, 2H), 1.98-1.96 (m, 4H), 1.79-1.77(m, 2H). MS (ES, m/z): 715 [M+H]⁺.

Example 4 Procedure for the Measurement of NaP2b-Mediated P_(i)Transport

Materials.

HEK293 cells were obtained from the American Type Culture collection andpropagated per their instructions. Expression clones for rat and humanNaP2b (SLC34A2) were obtained from Open Biosystems (Catalog numbersMRN1768-9510282, and MHS1010-99823026, respectively). The sequence ofthe human protein was mutated to insert a threonine after residue 37,and to introduce a N39D mutation.

Inhibition of P_(i) Transport.

The rate of phosphate (Pi) uptake into HEK293 cells was measured using amodification of the method described by Mohrmann et al. (Mohrmann, I.,Mohrmann, M., Biber, J., and Murer, H. (1986) Am. J. Phys. 250(3 Pt1):G323-30.) Transfected HEK293 cells were treated with apharmacological agent to minimize endogenous PiT-mediated phosphatetransport activity, such that the only remaining sodium-dependentphosphate transport activity is that which was bestowed by introductionof the NaP2b genes.

Cells were seeded into 96-well plates at 25,000 cells/well and culturedovernight. Lipofectamine 2000 (Invitrogen) was used to introduce theNaP2b cDNA, and the cells were allowed to approach confluence during asecond overnight incubation. Medium was aspirated from the cultures, andthe cells were washed once with choline uptake buffer (14 mM Tris, 137mM choline chloride, 5.4 mM KCl, 2.8 mM CaCl₂, 1.2 mM MgSO₄, 100 uMKH₂PO₄, 1 mg/mL Bovine Serum Albumin, pH 7.4). Cells were then overlayedwith either choline uptake buffer or sodium uptake buffer (14 mM Tris,137 mM sodium chloride, 5.4 mM KCl, 2.8 mM CaCl₂, 1.2 mM MgSO₄, 100 uMKH₂PO₄, PiT-silencing agent, 1 mg/mL Bovine Serum Albumin, pH 7.4)containing 6-9 uCi/mL ³³P orthophosphoric acid (Perkin Elmer) and testcompound. Each compound was tested at twelve concentrations ranging from0.1 nM to 30 uM. Assays were run in duplicate.

After incubation for 3-30 minutes at room temperature, assay mixtureswere removed, and the cells were washed twice with ice cold stopsolution (137 mM sodium chloride, 14 mM Tris, pH 7.4). Cells were lysedby addition of 20 μL 0.1% Tween 80 followed by 100 μL scintillationfluid, and counted using a TopCount (Perkin Elmer).

pIC50 (the negative log of the IC50) values of the test compounds werecalculated using GraphPad Prism. Preliminary studies showed that underthese conditions, sodium-dependent Pi uptake was linear for at least 30min and tolerated 0.6% (v/v) DMSO without deleterious effects.

To ascertain if an inhibitor was competitive for binding with phosphate,the procedure was repeated, but raising the concentration of thesubstrate in the assay mixture from 0.1 to 2.1 mM phosphate. Compoundsthat maintained their potency for inhibition of NaPi2b in the presenceof 2.1 vs 0.1 mM phosphate were considered to not be competitive withrespect to phosphate.

TABLE 1 Inhibitory activity of compounds against rat and human NaP2bvalues reported as pIC50. pIC50 range for pIC50 range Competitive withExample rat Nap2b for human* respect to Pi?** PFA 2-3 Yes 1 5.1-6.05.1-6.0 2 >6.0 >6.0 No 3 4.6-5.7 *A blank indicates not tested**Indicates compound is considered to not be competitive with respect tophosphate. A blank indicates not tested for competitive inhibition.

Example 5 In Vivo Evaluation Procedure Co-Dosing in Chow

Male, 7-week-old Sprague-Dawley rats (Charles-River laboratoriesinternational, Hollister, Calif.) were allowed to acclimate for aminimum of 3 days. The experiment was initiated by switching animals toa synthetic diet (0.6% phosphorus and 0.6% calcium, Harlan TekladTD.84122) for four days. After this time, the animals were placed intometabolic cages for daily monitoring of food and water consumption, aswell as urine and fecal collections. Test compounds were incorporatedinto the powdered diet listed above containing 3% chocolate flavoring(w/w, BioSery #7345) at 1.3 mg test compound per gram of diet to achievean average daily nominal dose of 100 mg/kg/day. The actual dose receivedby each animal was later determined by measuring prepared dietconsumption and body weight. Urine samples were collected in three dailyperiods from 24-48, 48-72, and 72-96 hours of drug dosing. Averagingthese three 24 h periods allows for the more representative measurementsof urination, fecal excretion, food consumption and water uptake foreach animal. Phosphorus levels in the urine were determined by anionexchange chromatography using a Dionex ICS-3000 ion chromatographysystem. Urine samples were diluted 1:500 or 1:1000 and injected onto anIonPac AS18 analytical column (2×250 mm) using a potassium hydroxideeluent. Elution of urine phosphate ions was monitored via conductivitydetector and reported as ppm relative to a standard ion solutioncontaining phosphate. Daily urinary P output relative to the P consumedin the prepared diet for each animal was calculated. The percentageinhibition of phosphorus absorption was estimated by determining thereduction of this ratio compared to the control group (animals with nodrug in chow). The differences between the means of control and treatedgroups were evaluated by t tests.

TABLE 2 Inhibition of uptake of phosphorus from the intestine asmeasured using the co-dosing in chow model Mean drug dose, Mean %inhibition Example mg/kg/day Urine Pout/P consumed t-test 2 115 20 *** *p < 0.05 versus control; ** p < 0.01 versus control; *** p < 0.001versus control

Example 6 Determination of Compound Cmax and AUC

Sprague-Dawley rats were orally gavaged with test article at a nominaldose of 2.5 or 10 mg/kg and blood was collected at 0.5, 1, 2 and 4 h.Blood samples were processed to plasma using K₂EDTA as ananticoaglulant. Plasma samples were treated with acetonitrile containingan internal standard, precipitated proteins removed by centrifugation.Supernatants were analyzed by LC-MS/MS and compound concentrations weredetermined by interpolated from a standard curve prepared in plasma.Table 3 illustrates data from the pharmacokinetic profiling of selectedexample compounds. All compounds were orally dosed at the dosage shown,and pharmacokinetic parameters determined.

TABLE 3 Pharmacokinetic profiling of representative compounds ActualOral AUC Dose LLOQ¹ Cmax (ng × Example (mg/kg) (ng/mL) (ng/mL) hr/mL) 17.5 10 299 433 2 11 0.5 91 <97.0 ¹LLOQ = Lower Limit of Quantification

Example 7 Fecal Recovery of Orally Administered Compounds

Quantitative determination of test compound level in feces after oralgavage was performed using the same set of animals used to determinetest compound concentration in plasma (Example 6). The animals were keptin metabolic cages and feces were collected from the time of dosinguntil 48 hr after dosing. Upon collection, feces was dried bylyophilization and ground to a visually homogenous powder. Duplicatesamples of ground feces from each individual animal were weighed out andextracted using organic solvent. Extracted samples were then dilutedinto mobile phase and test compound levels were quantitativelydetermined by LC-MS/MS analysis as described in Example 6 except thatthe standard curve was prepared in a feces matrix.

TABLE 4 Fraction of orally administered compound recovered in feces 48hours after dosing Example % recovered in feces 1 34 2 2.9

All of the U.S. patents, U.S. patent application publications, U.S.patent applications, foreign patents, foreign patent applications andnon-patent publications referred to in this specification areincorporated herein by reference, in their entirety to the extent notinconsistent with the present description.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A compound having the following structure (I):

or a stereoisomer, prodrug or pharmaceutically acceptable salt thereof,wherein: X is substituted aryl or substituted heteroaryl; Y is halogen,optionally substituted alkylamino, optionally substituted alkoxy,optionally substituted thioalkyl, optionally substituted cycloalkyl,optionally substituted heterocyclyl, optionally substituted: aryl,—O(optionally substituted cycloalkyl), —O(optionally substitutedheterocyclyl) or —O(optionally substituted aryl); each R₁ is,independently, hydrogen, halogen, C₁₋₆alkyl or C₁₋₆haloalkyl; and R₂ ishydrogen or optionally substituted C₁₋₆alkyl.
 2. A compound of claim 1wherein Y is halogen.
 3. A compound of claim 2 wherein Y is chloro.
 4. Acompound of claim 1 wherein Y is alkylamino.
 5. A compound of claim 4wherein Y is diethylamino.
 6. A compound of claim 1 wherein Y is alkoxy.7. A compound of claim 1 wherein Y is heterocyclyl.
 8. A compound ofclaim 7 wherein Y is 1-piperidinyl and the compound has the structure:


9. A compound of claim 1 wherein Y is —O(cycloalkyl).
 10. A compound ofclaim 1 wherein X is —ZR₃, and wherein Z is aryl or heteroaryl and R₃ isa non-hydrogen substituent.
 11. A compound of claim 10 wherein Z isaryl.
 12. A compound of claim 11 wherein Z is phenyl.
 13. A compound ofclaim 12 wherein the compound has the structure:


14. A compound of claim 10 wherein Z is heteroaryl.
 15. A compound ofclaim 14 wherein Z is pyridinyl.
 16. A compound of claim 15 wherein thecompound has the structure:


17. A compound of claim 10 wherein R₃ is: (a) —CH₂S(O)₀₋₂(optionallysubstituted C₁₋₆alkyl)C(═O)NR₇R₄, (b) —CH₂S(O)₀₋₂(optionally substitutedC₁₋₆alkyl)NR₇R₄, (c) —CH₂S(O)₀₋₂(optionally substitutedC₁₋₆alkyl)C(═O)OR₅, (d) —CH₂S(O)₀₋₂(optionally substitutedC₁₋₆alkyl)OR₅, (e) —CH₂S(O)₀₋₂(optionally substituted C₁₋₉alkyl)R₆, (f)—CH₂S(O)₀₋₂R₆, (g) —CH₂S(O)₀₋₂NR₇R₄, (h) —CH₂S(O)₀₋₂(CH₂CH₂O)_(x)R₅, (i)—CH₂NR₂(CH₂CH₂O)_(x)R₅, (j) —C(═O)NR₇(optionally substitutedC₁₋₆alkyl)C(═O)NR₇R₄, (k) —C(═O)NR₇(optionally substitutedC₁₋₉alkyl)NR₇R₄, (l) —C(═)NR₇(optionally substituted C₁₋₆alkyl)C(═O)OR₅,(m) —C(═O)NR₇(optionally substituted C₁₋₆alkyl)OR₅, (n)—C(═O)NR₇(optionally substituted C₁₋₆alkyl)R₆, or (o)—C(═O)NR₇(CH₂CH₂O)_(x)R₅, wherein R₄ is hydrogen, hydroxyl, alkoxy,optionally substituted C optionally substituted aryl, optionallysubstituted heterocyclyl or optionally substituted heteroaryl; R₅ ishydrogen, optionally substituted C₁₋₆alkyl, optionally substituted aryl,optionally substituted heterocyclyl or optionally substitutedheteroaryl; R₆ is optionally substituted aryl, optionally substitutedheterocyclyl or optionally substituted heteroaryl; R₇ is hydrogen oroptionally substituted C₁₋₆alkyl; and x is an integer from 2 to
 10. 18.A compound of claim 1 wherein each R₁ is hydrogen.
 19. A compound ofclaim 1 wherein R₂ is hydrogen.
 20. A compound of claim 1 wherein R₂ isan optionally substituted C₁₋₆alkyl.
 21. A compound of claim 20 whereinR₂ is trifluoromethyl.
 22. A pharmaceutical composition comprising acompound of claim 1, or a stereoisomer, pharmaceutically acceptable saltor prodrug thereof, and d pharmaceutically acceptable carrier, diluentor excipient.
 23. The pharmaceutical composition of claim 22, furthercomprising one or more additional biologically active agents.
 24. Thepharmaceutical composition of claim 23, wherein the additionalbiologically active agent is selected from vitamin D₂, (ergocalciferol),vitamin D₃ (cholecalciferol), active vitamin D (calcitriol) and activevitamin D analogs (e.g. doxercalciferol, paricalcitol).
 25. Thepharmaceutical composition of claim 23, wherein the additionalbiologically active agent is a phosphate binder, and the compound doesnot interfere with the phosphate binder.
 26. The pharmaceuticalcomposition of claim 25, wherein the phosphate binder is selected fromthe group consisting of Renvela, Renagel, Fosrenol, calcium carbonate,calcium acetate (e.g. Phoslo), Zerenex™ Fermagate, APS1585, SBR-759 andPA-21.
 27. The pharmaceutical composition of claim 22, wherein thecompound is substantially active as an inhibitor of Na/phosphateco-transport and the Na/phosphate co-transport is mediated by NaPi2b.28. A method of inhibiting phosphate transport in a mammal, comprisingadministering to the mammal an effective amount of a compound ofclaim
 1. 29. The method of claim 28, wherein the method inhibitssodium-mediated phosphate uptake.
 30. The method of claim 28, whereinthe method is selected from the group consisting of: (a) a method fortreating hyperphosphatemia; (b) a method for treating a renal disease;(c) a method for delaying time to dialysis; (d) a method for attenuatingintima localized vascular calcification; (e) a method for reducing thehyperphosphatemic effect of active vitamin D; (f) a method for reducingFGF23 levels; (g) a method for attenuating hyperparathyroidism; (h) amethod for improving endothelial dysfunction induced by postprandialserum phosphate; (i) a method for reducing urinary phosphorous: (j) amethod for normalizing serum phosphorus levels; (k) a method fortreating proteinura; and (l) a method for reducing serum PTH andphosphate concentrations or levels.
 31. The method of claim 30, whereinthe renal disease is chronic kidney disease or end stage renal disease.32. A method of treating hyperphosphatemia in a mammal in need thereof,comprising administering to the mammal an effective amount of a compoundof claim 1.